Archive for November, 2009
Build Muscle Mass And Strength: The Truth About Building Muscle
“The Truth About Building Muscle” by Sean Nalowanyj is a common sense fitness and nutrition program that shows you how to build muscle mass, increase strength and burn off excess body fat.
The muscle-building program is based on the law of progressive overload and shows you how to use more weight with more repetitions to build strength as quickly as possible. By cycling a specific series of weight lifting exercises and following a sensible nutritional routine, you can build ripped muscles without the use of nutritional supplements, a personal trainer, high tech equipment or illegal drugs.
Some of the secrets “The Truth About Muscle Building” will reveal include:
* The way to build strong, ripped muscles in just 2 hours and 45 minutes each week.
* Why gaining strength is the single most important factor for gaining muscle.
* The reason why popular terms such as “the burn” and “pump” really don’t work.
* How to calculate your own perfect diet based on your goals, along with the exact amounts of carbohydrates, protein, water and fats to maximize your ability to build muscle.
* The secret of how to block out muscle pain for a completely beneficial workout every time.
* How to keep your body in a constant anabolic state to build muscle 24 hours a day.
* The proper techniques and cycling for weight training routines.
* Effective, 15 minute cardio workouts that burn fat without losing muscle.
* How you can use the critical three hours after you workout to propel weight gain.
* Unbiased reviews of 20 of the leading body-building supplements.
All of these techniques are outlined in everyday language that is easy to understand. The 249 page eBook also comes with 7 supplemental bonus gifts, which make it easier for you to develop your fitness and nutritional routine based upon your personal goals:
* 26 Week Workout Plan and Printable Log Book;
* Full Exercise Database featuring full motion video of over 100 of the most effective weight lifting exercises;
* Three months of personal, one-on-one email support with 24 hour responses from Sean himself;
* Online Muscle Building Video Lesson Series;
* “The Top 12 Mistakes Revealed”, an MP3 audio course;
* MGT Progress Tracker 6000, a 3 month membership to a software that you can use to track every detail of your individual muscle building program;
* Lifetime ebook updates.
So if you’re looking to build muscle mass and strength, you might want to consider trying “The Truth About Building Muscle.”
This unique weight lifting and nutritional program allows you to customize a program to build strong muscles and burn fat without supplements, subscriptions or a personal trainer. The program features outstanding support, including personalized online advice from its creator, at a realistic price.
The result is incredible muscle growth and strength that you didn’t even know was possible.
Ryan Cote
http://www.articlesbase.com/health-articles/build-muscle-mass-and-strength-the-truth-about-building-muscle-133651.html
Heath Benefits Of Cycling 15 Minutes A Day
When done properly, cycling is an effective and enjoyable form of aerobic exercise. Cycling can reduce the risk of heart disease, high blood pressure, obesity and diabetes according to a report by Kelley GA. Effects of Aerobic exercise in normotensive adults, 1995. It can reduce your ‘real age’, lowering it more than a decade lower than your chronological age.
The indirect health benefits include reducing serious injuries caused by falls in older people, osteoporosis, and hip fractures.
Statistics show that cyclists, even those who only travel short distances can reduce the risk of death by 22 per cent.
Optimum results are achieved when cyclists are breathing heavily, but are not out of breath. Exercise has been shown to increase HDL (”good” cholesterol) and reduce the amount of triglycerides in the blood. Again, this means improved cardiovascular health. This leads to a reduced chance of heart blockage and reduces the risk of stroke. There are some reports that link exercise to a lowered risk of developing some cancer, like colon cancer.
Cycling burns the calories in a chocolate bar or a couple of alcoholic drinks in one hour, 300 calories. Translated into modern lifestyle terms, a fifteen-minute bike ride, five times a week, burns off 11 pounds of fat a year and meets the requirements for reducing heath risks.
There is a trick to exercising. Running a nine-minute-mile burns 11 calories a minute. Walking at 18 minutes per mile burns five. Faster exercise burns more calories.
Exercise continues to burn fat after the workout ends. Once the sweating stops the body’s metabolisms remains high. You can you increase the post-exercise burn?
A few scientific studies suggest that exercising for 20 minutes at 35 to 55% of aerobic capacity, as in riding briskly, elevated metabolism for 20 minutes after stopping. That means that a 20 minute, brisk bike ride burns fat for 40 minutes.
Cycling has been proven to reduce stress and depression and relieve symptoms of premenstrual syndrome.
The Department of Transport reports that ‘even a small amount of cycling can lead to significant gains in fitness’. The study reveals that aerobic fitness was boosted by 11 per cent after six weeks of cycling ’short distances’ four times a week and cycling four miles a day the aerobic benefit increased to 17 per cent.
The Fentem PH. ABC of sports medicine report, Benefits of exercise in health and disease, 1994 concludes that cycling is ‘one of the few physical activities which can be undertaken by the majority of the population as part of a daily routine’.
The choice of bike is a personal thing.
Most people never cycle more than five miles, so choosing an expensive bike designed to challenge the most adventurous dare devils. Instead, choose a bike that will manage the local terrain, comfortably.
Equipment needs will also vary. Older people should consider elbow and knee guards. These will help prevent debilitating joint injuries that can seriously limit your mobility. A helmet is not optional.
Do not buy a helmet from a local hardware store. Get one from a bicycle specialty store. The selection is larger, and the quality better. Shopping at an online store can also save money.
Once introduced into the bicyle riding community, you’ll soon set out on your daily cycle for the joy of it. Health benefits will be secondary
Chip Clark
http://www.articlesbase.com/sports-and-fitness-articles/heath-benefits-of-cycling-15-minutes-a-day-104230.html
The Hamster School Of Management
It can be said that everything you needed to know in life you learnt in kindergarten. “Don’t take what is not yours “and “Always tell the truth”.
Yet many people do not understand what you might consider to be perfectly clearly basic truths of life that are clearly understood and fully comprehended your four year old. That is to “Tell the truth” and “Not to take what is Not Yours”.
These are the simple basics of a happy and secure life. In most cases you learnt them by example- either by a close family member or another very important example in your life.
Many people you will meet in your travels may repeat simple phrases and slogans such as “Those that do not plan – plan to fail” or such truisms as “The job is not done until the tools (or paperwork) is either put away or finished.
Yet the amazing thing is that most of these same people do not comprehend simple truths that you as child learnt. It is amazing that even a hamster seems to know such things intuitively and instinctively.
How can this be? Why is it that apparently intelligent or in many cases non intelligent people cannot grasp these simple and apparent truisms.
The answer comes down to two factors. Firstly the examples these people saw in life whether it was from their home and family environment or other important role models.
It is most important that you set good role models in your parenting skills.
Secondly in life and in many job or power structures a person is promoted not to the station that he or she is best at or most competent but rather to the stage at which his terrible incompetence stops them and their progress up the ladder of life..
Think of it who is it that influenced you to good worthwhile habits in life. What is a family member, an uncle a neighbor? This person may have inadvertently set you on the good path. It is much better to learn from a good role model than have to overcome the mistakes that a poor role model will leave you to overcome
Secondly it should be understood that in life people do not stop at their level of competence. Organizations whether it is at your place of work, your church, school or non profit group tend to promote people until even after trouble begins. Organizational structure is such people are seldom trained for their jobs. They are thrust into a position that they are not trained for and bumble through. To make it worse their role model of choice is their previous poorly or untrained processor… This cycle of life goes on and on infinitum.
Winston Churchill said democracy is the worst form of government except all the others that have been tried. The same can be said for role models in life. The same parallels can be said about the job site and parenting skills. It is amazing that there are not more homicides in the workplace among staff and management.
William Z. Piker
http://www.articlesbase.com/management-articles/the-hamster-school-of-management-121724.html
Baby Walkers Guidelines
Looking for a unique gift for your child grows? Many gift ideas are available in the market that is fabulous and exquisite. But if your child has a keen on sports cars then junior rally driving is perfect gift for him. The driving experience is full of fun and excitement that will last forever. Junior rally driving is an excellent opportunity for children to experience the conduct of certain sports cars. Any rally driving experience begins with an introduction on the car and the activity. A professional rally driver will provide information on what techniques are used in conducting the rally. Participants are also enriched with details why the methods are used and how they can exercise them. Thus, the instructor gives participants the basic knowledge of what is behind the wheel.
The experience of the junior rally driving is the life. Participants have the opportunity to lead class and fast sports cars that can be spotted in magazines or on television. Junior rally driving is a guarantee of safety and driving experience for children and all the rally cars are built to specification and competition are maintained at the highest level. Throughout this experience, the instructors as part of the co-pilot and the guide on the stage, teaching driving techniques such as hand turns, opposite lock power slides. Junior rally driving experience is available for a session or period. Many driving sessions are available on certain days (Saturday or Sunday).
The junior rally driving are available for children over 4ft 10 (148cm) and over 12 years. On the other hand, for passenger rides the minimum height of the participant should be 4ft5 (135cm). Before the first cycle of courses (other terms and conditions) all parents must sign a form of compensation on behalf of the child. This rally driving for young people is also an ideal gift for your children to enjoy their birthday or for inspiration.
Opponents of the proposed ban stairs cause argue that most of the injuries, not hikers. But since it is impossible to eliminate the stairs, you are advised to stop using walkers, “said the drafting of the Health News.
To allay consumer groups, some manufacturers have revised their walkers and have developed security devices. Yet the fact remains that many hikers are dangerous and pose a threat to your child.
If your child does not have a walker, do not make the mistake of buying one. If you decide to get one, choose a model that is too large to fit through the door and pay particular attention to your child. In Consumer Reports’ Guide to Baby Products, Sandy Jones and Werner Freitag offers the following advice:
Remove the stroller wheels to prevent children from going too quickly and make them more prone to accidents.
Never leave children unattended.
Never use hikers near the stairs, steps, or thresholds. Make sure the surfaces are flat and free of objects that cause May trigger inside or outside.
To reduce the chances of the child from sliding across the seat, to check that the two feet of the child from touching the ground, and never wear the marchers of the child in it.
Manseo Sharma
http://www.articlesbase.com/health-articles/baby-walkers-guidelines-724320.html
Introduction to Plc and Scada
Introduction to PLC’s
Programmable Logic Controllers
Bedford Associates, founded by Richard Morley introduced the first Programmable Logic Controller in 1968. This PLC was known as the Modular Digital Controller from which the MODICON company derived its name. The History of the PLC as told to Howard Hendricks by Dick Morley provides an interesting insight into the early development of the PLC.
Schnieder Quantum PLC
Programmable Logic Controllers were developed to provide a replacement for large relay based control panels. These systems were inflexible requiring major rewiring or replacement whenever the control sequence was to be changed.
The development of the micro processor from the mid 1970’s have allowed Programmable Logic Controllers to take on more complex tasks and larger functions as the speed of the processor increased.
Ladder Logic
PLC had to be maintainable by technicians and electrical personnel. To support this the programming language of Ladder Logic was developed. Ladder Logic is based on the relay and contact symbols technicians were used to through wiring diagrams of electrical control panels.
Until recently there has been no formal programming standard for PLC’s. The introduction of the IEC 61131 Standard in 1998 provides a more formal approach to coding. PLC Manufacturers have so far been slow on the uptake of the standard with partial implementation. The SearchEng articleIEC 61131-3, a Standard for PLC Software by R.W. Lewis provides an introduction to the standard.
The documentation for early PLC Programs was either non existent or very poor, just providing simple addressing and basic comments, making large programs difficult to follow. This has been greatly improved with the development of PLC Programming Packages.
SCADA and HMI
The early programmable logic controllers interfaced with the operator in much the same way as the relay control panel, via push-buttons and switches for control and lamps for indication.
The introduction of the Personal Computer (PC) in the 1980’s allowed for the development of a computer based interface to the operator, these where initially via simple Supervisory Control and Data Acquisition (SCADA) systems and more recently via Dedicated Operator Control Panels, known as Human Machine Interfaces (HMI).
The History of the PLC
as told to Howard Hendricks by Dick Morley
The following are some fables associated with the first ten years of the programmable controller business. These Fables may or may not have a basis of truth, but in general, they are the best that my Alzheimer-plagued memory can do at the moment. As has been often in other articles and reports, the startup of Modicon and the programmable controller industry as a whole is well documented. The programmable controller was detailed on New Year’s Day, 1968, and from hence till now, a slow steady growth has allowed the manufacturing and process control industries to take advantage of applications-oriented software.
The early days however, were not as straightforward nor as simple. We had some real problems in the early days of convincing people that a box of software, albeit cased in cast iron, could do the same thing as 50 feet of cabinets, associated relays and wiring. The process was indeed difficult, and deserves some of the stories that I hope the reader will be regaled with as he proceeds onward through the tortuous swamp of my mind.
One of my earliest recommendations was that the programmable controller, according to my own system architecture specification, did not need to go fast because I felt as though speed was not a criteria because it would go as fast as we needed it to. The initial machine, which was never delivered, only had 125 words of memory, and speed was not a criteria as mentioned earlier. You can imagine what happened! First, we immediately ran out of memory, and second, the machine was much too slow to perform any function anywhere near the relay response time. Relay response times exist on the order of 1/60th of a second, and the topology formed by many cabinets full of relays transformed to code is significantly more than 125 words. We expanded the memory to 1K and thence to 4K. At 4K, it stood the test of time for quite a while. Initially, marketing and memory sizes were sold in 1K, 2K, 3K, (?) and 4K. the 3K was obviously the 4K version with constrained address so that field expansion to 4K could easily be done.
The question of speed, in part, was part of the early designs. No interrupts were necessary because the external signal conditions were directly written onto memory without any supervisory requirements or “operating system of the conventional type. This allowed the processor to pay attention to solving logic rather than housekeeping the I/O. As a result, of course, the processor had to have significantly more processing power than normally associated with this size computer; and secondly, the system had to be made to run fast.
We increased the memory size, as mentioned above, but to get it to run fast, we had to break up the machine into three distinct components. Initially, the programmable controller was conceived of a processor board and a memory, and that the algorithmic and logical manipulation would be done in software. This approach was painfully slow, both on the generic “store bought computers, and other items.
We did, however, manage to substantially speed up the machine by making a third major component. This was called the logic solver. A logic solver board solved the dominant algorithms associated with solving ladder logic without the intervention and classical software approach of general-purpose processing. This meant that we ended up with three boards; memory, logic solver and processor. This single step allowed us to get the speed we needed in this application-specific computer to solve the perceptually simple problem of several cabinets full of relay wiring.
We had also assumed a modular approach to the programmable controller. In act, the name Modicon means MOdular DIgital CONtroller. The modularity, however, was soon abandoned because, as everyone knows, open architectures are no good. We instead had the marketing premise that a large footprint would contain within it the sets of problems we wished to solve. This meant that a buyer of programmable controllers could buy large numbers of the same units, and the software and hardware would be identical across a broad spectrum of applications in his factory. Service, maintenance and total life cost would be substantially lower than the perceived lower cost of an open architecture and modular expansion. Although at first, a supporter of the open architecture modular expansion, I soon became convinced by the marketplace, but this was folly.
We took one of our early units which was aimed at the machine tool industry because of my Bedford Associates consulting background, up to one of the early requesters of this equipment. This particular early requester was Byrant Chuck and Grinder in Springfield, Vermont. We took the machine up there, and it was heavy. This was the 084. The 084 was in the trunk of my old Pontiac, and since we needed help carrying it in, requested some of the people at Bryant to help us. We went out and opened the hood, and the first comment made by an outside viewer of the programmable controller said, “Thank God it,s not another pastel colored piece of sheet metal.
We can hypothesize from this particular comment that the ruggedness of the visual design was pleasing to him, and being human (as opposed to Martian), assumed that this same attitude went deep inside the construction of the machine in both the hardware and software. Indeed, this was the case, and the machine as a result, was built rugged, had no ON/OFF switch, had no fans, did not make any noise and had no wear out system.
To reminisce for a moment—in selecting the cores for the first memories, which in itself was a revolutionary step, we selected these cores and we applied Shannon,s Law. Shannon,s Law assumes that the signal-to-noise ratio is what makes signals good or bad. There are several ways to get the power from the signal-to-noise ratio; one is to code heavily, be triply redundant, and use lots and lots of error checking. There is another way, which is perfectly compatible with theory, which is to use lots of signal power in another domain. A nice switch, a car battery and a D-rated light bulb will work fairly well over a long time period.
Therefore, what we did was rather than going error checking, triply redundant and stuff, we got, and searched for and found high energy, large ferrite core memories that had lots on energy per bit. We still make the same assumption today. The energy per bit is extremely important—as Shannon,s theory said in his most famous 1948 paper, that the signal noise to power noise is what gives you transmission. the way we got signal power was to increase the energy per bit. This we felt was far more important than getting the energy per bit increased by means of doubly transmitting it. But I digress. Bryant Chuck and Grinder put it in, and liked the equipment so much that they never bought one. They in turn thought it was a good idea, and as many did at that time, tried to evolve their own.
One of our first major customers, however, was Landis in Landis, PA. We flew the equipment down in a private aircraft, and with apprehension because we were late (as usual), brought the equipment into Landis. In doing so, we tripped over the threshold. The equipment went KA-RASH onto the floor! Without much chagrin, we picked the equipment up, trundled it in. hooked it up, and low and behold, it worked quite well.
Now, Landis was pleased and surprised. They were pleased because it worked, but they were most pleasantly surprised—not because the equipment worked—but because the guys from Modicon fully expected the equipment to work in spite of it being dropped. In other words, the people from Modicon weren,t nervous about the fact that it fell on the floor over the threshold.
Landis subsequently took and wrapped welding coils of wire around the machine to induce electro-magnetic noise to see if they could make it fail. We had them there! We used to test the programmable controllers with a Teslar coil that struck a quarter inch to half-inch arch anywhere on the system, and the programmable controller still had to continue to run. There was significant strangeness with respect to the programmable controller. For example, it had no ON/OFF switch. It had no means to load software. It had no fans. It ran cool. It could survive bad, physical and thermal environments. It was not computer industry standard. There were many things that were most difficult in the acceptance of the programmable controller, and early acceptance was most difficult indeed.
Our sales in the first four years were abysmal. Early innovators such as Landers and General Motors were, of course, heroes to our eyes, but they would buy small numbers of units and then test them in the field before they committed themselves later on. We had one customer in the utilities business that took them approximately six to seven years to make a decision to but the first one.
We never really sold any programmable controllers into the intended market which was machine tool control such as lathes, grinders and stuff, but we did, as luck would have it, stumble across the transfer line market which was and still is the mainstay, long-term market for the application of programmable controllers. Discreet parts manufacturing in an automatic environment, i.e., mass production, continues to be, and probably will be for the future, the mainstay of the programmable controller industry.
Some of the more interesting stories center around the personalities and experiences as opposed to the programmable controller. Modicon,s third president (or fourth, if you count my two-week stint) was Don Kramer. When Don Kramer was chosen as president, we decided to go out and celebrate at the Lanum Club in Andover. At the time, we felt we should celebrate over both martinis and food. As we were leaving the shop for the Lanum Club, Don made the aside comment that “the place is dingy and needs a paint job. As we were leaving, I mentioned to Don that as president you have to change what you say, and not be very open—you have to be a little careful about what you say because employees, customers, and boards of directors tend to take what you say as truth. Rather than listen to the meaning, they listen to the literal statements, and one must be careful. We went over to the Lanum Club and had a nice glowing two hours of discussion, food, and drink. Coming back, as we entered the Modicon lobby, we noticed that there was scaffolding about and people were painting. We went over and asked Lou as to why these people are painting since, at the time, we don,t have any money. Who ordered this paint job? And Lou looked Don Kramer straight in the eye, and said, “Why you did, Mr. Kramer. Nuff said.
As has been mentioned many times, your author, that,s me—Dick Morley—is supposed to be the inventor of the programmable controller. This is at best, partially true. The thing that made the Modicon company and the programmable controller really take off was not the 084, but the 184. The 184 was done in design cycle by Michael Greenberg, one of the best engineers I have ever met. He, and Lee Rousseau, president and marketeer, came up with a specification and a design that revolutionized the automation business. they built the 184 over the objections of yours truly. I was a purist and felt that all those bells and whistles and stuff weren,t “pure, and somehow they were contaminating my “glorious design, Dead wrong again, Morley! they were specifically right on! the 184 was a walloping success, and it—not the 084, not the invention of the programmable controller—but a product designed to meet the needs of the marketplace and the customer, called the 184, took off and made Modicon and the programmable controller the company and industry it is today. My compliments to the two chefs—Lee Rousseau and Mike Greenberg.
The issue of quality in programmable controllers is a story that is normally taken for granted. The gentle reader must remember that our engineering people came from the computer industry where reliability in those days was a phantom—a phantom of design, a phantom of cost. People felt that reliability was something other people did, and that if we only could deliver faster computers, even if they didn,t work, everything would be fine.
When the programmable controller was designed, it was designed in to be reliable. We used lots of energy per information bit by utilizing D-rated components, large memory ferrite cores, relatively stable and large etchings on printed circuit boards, totally enclosed systems and conductive cooling. No fans were used, and outside air was not allowed to enter the system for fear of contamination and corrosion. Mentally, we had imagined the programmable controller being underneath a truck, in the open, and being driven around—driven around in Texas, driven around in Alaska. Under those circumstances, we anted it to survive. The other requirement was that it stood on a pole helping run an utility or a microwave station which was not climate controlled, and not serviced at all. Under those circumstances, would it work for the years that it was intended to be? Could it be walled in? Could it be bolted in a system that was expected to last 20 years?
The humorous side of this is though we did all those designs and very carefully tried to make this system as intrinsically reliable as we could, not by redundancy, but by building well. In other words, it was designed to be built, it was designed to be designed, and it was designed to be reliable. We, however, as engineers, didn,t understand the accountants and manufacturing. those two have their grail, shipments by the end of the month. As far as we could ascertain at the time, shipments were made independent of quality and independent of whether or not the system ran.
In the early days of the programmable controller and Modicon, even though I wasn,t a direct employee and an owner, I would give out my home phone number to many of our critical customers so that if they had a problem, they could call me directly. Several calls indicated that when we shipped near the end of the month, let’s say October 34th, that the equipment would not run; and secondly, when they opened the box and took the machine apart, cards were missing, bolts were on the bottom of the cabinetry, and some of the cards were not fully inserted. In other words, to make the end of the month was much more important than to deliver equipment that ran. to put it mildly, we were pissed! How do we as engineers maintain quality without continual surveillance which is most difficult for the design and entrepreneurial mind set. What we did was specify and design “blue boxes. These were cabinetries that the system had to operate in and run continuously for a minimum of 24 hours, under load, and under varying conditions. The box was built out of plywood, but its primary intention was to heat cycle the programmable controller under various input/output loads. We also ran, as a specification, that a Tesla coil was to be used on the programmable controller, and that vibration and thumping with a hammer (rubber) would be part of the specification.
This may seem unscientific to many of you, but let us assume that you try to get your equipment to run while somebody purposely tries to destroy it with a rubber hammer or spark coil that he can put anywhere on the system. Remember, your intention is to make the processor stop. That combination significantly depressed those monthly shipments during the first period. As a result of that, however, the message got through. Not only did we build ovens and tests, and pay attention to heat and spark and RF emissions, we would run the system continuously even in the shipping crate to get the maximum number of pre-custom hours we could. It was important to us that we found the mistakes and not the customer and his secondary customer.
The language itself, ladder lister, bears some discussion. This particular language was not the invention of Modicon. We hypothesize that the language is very old, and originated in Germany to describe relay circuitry. If one looks at ladder lister, it has been our technical community for so long, we somehow think those little symboligies actually look like relays. In fact, it,s a mnemonic form of rule-based language, very modern and very high level, but designed in a Darwinian fashion over a period of many decades.
The ladder logic construct, “If… Then… is a very powerful construct used today in expert systems and other rule-based languages. The symbology, allowing normally open and normally closed situations as well as parallel and serial representation, was used for many decades before the invention of the programmable controller. I have worked on machines where the number of C-size and D-size prints were hung in special racks, and would be up to three feet thick worth of documentation on those drawing sets.
The name ladder comes from the fact that on the right-hand of the drawing is one power rail and the left-hand side is the other power rail; and in between in a horizontal fashion, is the statement or sequential connection of logical elements which we call relays or relay logic. The initial 084 had only logic in its functionality, and as a result, was marginal. In other words, all we did was replace relays rather than enhance the functionality by a factor of ten which is the entrepreneurial rule. Immediately, of course, based on customer response and our own frustrations, we put thing in the ladder listing language such as addition, multiplication, subtraction, and other functionalities that went far beyond relay capability and entered the realm of mathematics and set theory. This was still not sufficient, however, and we needed some way to make a “call to a “subroutine using ladder lister symbology and representation.
A software engineer, Chuck Schelberg, and myself were in the conference room one day trying to ascertain how we could make a generic call to functionalities that far exceeded the relay symbology and representation, and came up with the “DX function. This function was a block function that would be an element on the ladder logic representation that could perform many functionalities including arrays, motor drive functions, servo functions, extended mathematical functions, PID loops, ad nauseam. We felt there would be an occasional representation and use of these functionalities, and that not much had to be done to the programmable controller other than to modify the software. Wrong again!
The first customer that took delivery of a programmable controller utilizing the DX function, had a capability to be predictable and operate in real time. The RUN light went out, and the time to execute a scan or complete transformation of the ladder logic went far beyond the time allowable. Every single line had a DX function on it. Again we learned that when you enhance functionality, people use it all. I have never designed a computer that had too much memory. I,ve only designed computers that have too little memory. The same thing applies to any other functionality. Conventional wisdom seems to think that price/performance depends on only one thing—price—when, in fact, my experience has been that the customer cares little about price.
This price/performance tirade being over, one of the lessons we learned is that the customer wants functionality over the entire life cycle cost installation of the job. the customer also wants ease of installation, to have some fun, and to be proud of the work he does. After he,s finished, he never wants to come back.. The equipment should work as installed and as based. At one time, the programmable controller meantime before failure in the field was 50,000 hours. This is far in excess of almost any other type of electronic or control equipment.
The concept of languages and high-level languages is important. The programmable controller, as it evolved, began to request more and more power, and more and more memory. The memories continually went up as well as power. It is estimated that at one time, in the mid-1970s, that the programmable controller had the equivalent of two MIPS processor and 128 kilobytes of memory, which at that time was a significantly powered minicomputer capability. Why? High-level languages require power to run them. If we take the equivalent of the ladder lister statement “If… Then…, the high-level language as represented here, requires a substantial amount of interpretive compiler, if you will, generation of underlying code. In other words, this statement spawns significant underlying code that must be run quickly, reliably, and contain within it, all aspects of resource allocation and operations resource. The higher level the language, the more powerful the processor apparently has to be in order to run the language. Ladder lister is a high-level rule-based language which, until now, we haven,t talked much about in these terms. Our customers treated the programmable controller as a box of relays, and well they should. Language theory is neither necessary not desirable for most of the customers to know. The customers, instead, understand their problem, and are indeed much smarter than the design engineers because the dimensions of their problem far exceed the relatively simple problem of designing a computer software system and language. Ladder lister requires high performance which is one of the reasons it has difficulty running on the personal computer even of today
INTRODUCTION TO SCADA
SCADA is the abbreviation for Supervisory Control And Data Acquisition. It generally refers to an industrial control system: a computer system monitoring and controlling a process. The process can be industrial, infrastructure or facility based as described below:
Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, and large communication systems.
Facility processes occur both in public facilities and private ones, including buildings, airports, ships, and space stations. They monitor and control HVAC, access, and energy consumption.
A SCADA System usually consists of the following subsystems:
A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator monitors and controls the process.
A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process
Remote Terminal Units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.
Communication infrastructure connecting the supervisory system to the Remote Terminals Units
There is, in several industries, considerable confusion over the differences between SCADA systems and Distributed control systems (DCS). Generally speaking, a SCADA system usually refers to a system that coordinates, but does not control processes in real time. The discussion on real-time control is muddied somewhat by newer telecommunications technology, enabling reliable, low latency, high speed communications over wide areas. Most differences between SCADA and Distributed control system DCS are culturally determined and can usually be ignored. As communication infrastructures with higher capacity become available, the difference between SCADA and DCS will fade.
Systems concepts
The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything between an industrial plant and a country). Most control actions are performed automatically by remote terminals units (”RTUs”) or by programmable logic controllers (”PLCs”). Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.
Data acquistion begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required. Data is then compiled and formatted in such a way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls. Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing.
SCADA systems typically implement a distributed database, commonly referred to as a tag database, which contains data elements called tags or points. A point represents a single input or output value monitored or controlled by the system. Points can be either “hard” or “soft”. A hard point represents an actual input or output within the system, while a soft point results from logic and math operations applied to other points. (Most implementations conceptually remove the distinction by making every property a “soft” point expression, which may, in the simplest case, equal a single hard point.) Points are normally stored as value-timestamp pairs: a value, and the timestamp when it was recorded or calculated. A series of value-timestamp pairs gives the history of that point. It’s also common to store additional metadata with tags, such as the path to a field device or PLC register, design time comments, and alarm information.
Human Machine Interface
A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.
An HMI is usually linked to the SCADA system’s databases and software programs, to provide trending, diagnostic data, and management information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides.
The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled. For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.
The HMI package for the SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.
An important part of most SCADA implementations are alarms. An alarm is a digital status point that has either the value NORMAL or ALARM. Alarms can be created in such a way that when their requirements are met, they are activated. An example of an alarm is the “fuel tank empty” light in a car. The SCADA operator’s attention is drawn to the part of the system requiring attention by the alarm. Emails and text messages are often sent along with an alarm activation alerting managers along with the SCADA operator.
Hardware solutions
SCADA solutions often have Distributed Control System (DCS) components. Use of “smart” RTUs or PLCs, which are capable of autonomously executing simple logic processes without involving the master computer, is increasing. A functional block programming language, IEC 61131-3, is frequently used to create programs which run on these RTUs and PLCs. Unlike a procedural language such as the C programming language or FORTRAN, IEC 61131-3 has minimal training requirements by virtue of resembling historic physical control arrays. This allows SCADA system engineers to perform both the design and implementation of a program to be executed on an RTU or PLC. Since about 1998, virtually all major PLC manufacturers have offered integrated HMI/SCADA systems, many of them using open and non-proprietary communications protocols. Numerous specialized third-party HMI/SCADA packages, offering built-in compatibility with most major PLCs, have also entered the market, allowing mechanical engineers, electrical engineers and technicians to configure HMIs themselves, without the need for a custom-made program written by a software developer.
Remote Terminal Unit (RTU)
The RTU connects to physical equipment. Typically, an RTU converts the electrical signals from the equipment to digital values such as the open/closed status from a switch or a valve, or measurements such as pressure, flow, voltage or current. By converting digital setpoints to electrical signals and sending these electrical signals out to equipment the RTU can control equipment, such as opening or closing a switch or a valve, or setting the speed of a pump.
Quality SCADA RTUs have these characteristics:
Data Networking capability
Data Reliability
Data Security.
Supervisory Station
The term “Supervisory Station” refers to the servers and software responsible for communicating with the field equipment (RTUs, PLCs, etc), and then to the HMI software running on workstations in the control room, or elsewhere. In smaller SCADA systems, the master station may be composed of a single PC. In larger SCADA systems, the master station may include multiple servers, distributed software applications, and disaster recovery sites. To increase the integrity of the system the multiple servers will often be configured in a dual-redundant or hot-standby formation providing continuous control and monitoring in the event of a server failure.
Initially, more “open” platforms such as Linux were not as widely used due to the highly dynamic development environment and because a SCADA customer that was able to afford the field hardware and devices to be controlled could usually also purchase UNIX or OpenVMS licenses. Today, all major operating systems are used for both master station servers and HMI workstations.
Operational philosophy
For some installations, the costs that would result from the control system failing is extremely high. Possibly even lives could be lost. Hardware for some SCADA systems is ruggedized to withstand temperature, vibration, and voltage extremes, but in most critical installations reliability is enhanced by having redundant hardware and communications channels, up to the point of having multiple fully equipped control centres. A failing part can be quickly identified and its functionality automatically taken over by backup hardware. A failed part can often be replaced without interrupting the process. The reliability of such systems can be calculated statistically and is stated as the mean time to failure, which is a variant of mean time between failures. The calculated mean time to failure of such high reliability systems can be on the order of centuries.
Communication infrastructure and methods
SCADA systems have traditionally used combinations of radio and direct serial or modem connections to meet communication requirements, although Ethernet and IP over SONET / SDH is also frequently used at large sites such as railways and power stations. The remote management or monitoring function of a SCADA system is often referred to as telemetry.
This has also come under threat with some customers wanting SCADA data to travel over their pre-established corporate networks or to share the network with other applications. The legacy of the early low-bandwidth protocols remains, though. SCADA protocols are designed to be very compact and many are designed to send information to the master station only when the master station polls the RTU. Typical legacy SCADA protocols include Modbus RTU, RP-570, Profibus and Conitel. These communication protocols are all SCADA-vendor specific but are widely adopted and used. Standard protocols are IEC 60870-5-101 or 104, IEC 61850 and DNP3. These communication protocols are standardized and recognized by all major SCADA vendors. Many of these protocols now contain extensions to operate over TCP/IP. It is good security engineering practice to avoid connecting SCADA systems to the Internet so the attack surface is reduced.
RTUs and other automatic controller devices were being developed before the advent of industry wide standards for interoperability. The result is that developers and their management created a multitude of control protocols. Among the larger vendors, there was also the incentive to create their own protocol to “lock in” their customer base. A list of automation protocols is being compiled here.
Recently, OLE for Process Control (OPC) has become a widely accepted solution for intercommunicating different hardware and software, allowing communication even between devices originally not intended to be part of an industrial network.
Trends in SCADA
There is a trend for PLC and HMI/SCADA software to be more “mix-and-match”. In the mid 1990s, the typical DAQ I/O manufacturer supplied equipment that communicated using proprietary protocols over a suitable-distance carrier like RS-485. End users who invested in a particular vendor’s hardware solution often found themselves restricted to a limited choice of equipment when requirements changed (e.g. system expansions or performance improvement). To mitigate such problems, open communication protocols such as IEC870-5-101/104 and DNP 3.0 (serial and over IP) became increasingly popular among SCADA equipment manufacturers and solution providers alike. Open architecture SCADA systems enabled users to mix-and-match products from different vendors to develop solutions that were better than those that could be achieved when restricted to a single vendor’s product offering.
Towards the late 1990s, the shift towards open communications continued with individual I/O manufacturers as well, who adopted open message structures such as Modbus RTU and Modbus ASCII (originally both developed by Modicon) over RS-485. By 2000, most I/O makers offered completely open interfacing such as Modbus TCP over Ethernet and IP.
SCADA systems are coming in line with standard networking technologies. Ethernet and TCP/IP based protocols are replacing the older proprietary standards. Although certain characteristics of frame-based network communication technology (determinism, synchronization, protocol selection, environment suitability) have restricted the adoption of Ethernet in a few specialized applications, the vast majority of markets have accepted Ethernet networks for HMI/SCADA.
“Next generation” protocols such as OPC-UA, Wonderware’s SuiteLink, GE Fanuc’s Proficy and Rockwell Automation’s FactoryTalk, take advantage of XML, web services and other modern web technologies, making them more easily IT supportable.
With the emergence of software as a service in the broader software industry, a few vendors have begun offering application specific SCADA systems hosted on remote platforms over the Internet, for example, PumpView by MultiTrode. This removes the need to install and commission systems at the end-user’s facility and takes advantage of security features already available in Internet technology, VPNs and SSL. Some concerns include security, Internet connection reliability, and latency.
SCADA systems are becoming increasingly ubiquitous. Thin clients, web portals, and web based products are gaining popularity with most major vendors. The increased convenience of end users viewing their processes remotely introduces security considerations.
Security issues
The move from proprietary technologies to more standardized and open solutions together with the increased number of connections between SCADA systems and office networks and the Internet has made them more vulnerable to attacks. Consequently, the security of SCADA-based systems has come into question as they are increasingly seen as extremely vulnerable to cyberwarfare/cyberterrorism attacks.
In particular, security researchers are concerned about:
the lack of concern about security and authentication in the design, deployment and operation of existing SCADA networks
the mistaken belief that SCADA systems have the benefit of security through obscurity through the use of specialized protocols and proprietary interfaces
the mistaken belief that SCADA networks are secure because they are purportedly physically secured
the mistaken belief that SCADA networks are secure because they are supposedly disconnected from the Internet
Because of the mission-critical nature of a large number of SCADA systems, such attacks could, in a worst case scenario, cause massive financial losses through loss of data or actual physical destruction, misuse or theft, even loss of life, either directly or indirectly. Whether such concerns will cause a move away from the use of existing SCADA systems for mission-critical applications towards more secure architectures and configurations remains to be seen, given that at least some influential people in corporate and governmental circles believe that the benefits and lower initial costs of SCADA based systems still outweigh potential costs and risks] Recently, multiple security vendors, such as Byres Security, Inc., Industrial Defender Inc., Check Point and Innominate, and N-Dimension Solutions have begun to address these risks by developing lines of specialized industrial firewall and VPN solutions for TCP/IP-based SCADA networks. The problem according to Eric Byres, CEO of Byres Security, is that “while many infrastructure organizations are doing good work, others are falling behind. When you have this diversity of effort, you are only as effective as your weakest link.
Also, the ISA Security Compliance Institute (ISCI) is emerging to formalize SCADA security testing starting as soon as 2009. ISCI is conceptually similar to private testing and certification that has been performed by vendors since 2007, such as the Achilles certification program from Wurldtech Security Technologies, Inc. and MUSIC certification from Mu Security, Inc. Eventually, standards being defined by ISA SP99 WG4 will supersede these initial industry consortia efforts, but probably not before 2011.
N.Sankari
http://www.articlesbase.com/electronics-articles/introduction-to-plc-and-scada-679975.html
Self Defence: What Do You Think?
I am not a lawyer, I have no legal experience or skills. These are my opinions, but I hope they may be of use to you. To help you avoid problems.
As a keen sports (wo)man your interest may be cycling, running, gymnastics, whatever. It may even be the martial arts, karate, aikido, or any of a wide range of systems.
My concern here is that you may be out training by yourself, without a partner. Thus – at risk of being mugged or worse.
Possible? These days, probably Probable!
Consideration Number One – you are most definitely not allowed to carry a weapon to protect yourself against the risk of attack, or anything which can be construed as a weapon. Legal Fact! The measure is: Reasonability. Is it reasonable for you to be carrying a baseball bat when out on your bike? Or that ninja sword when going to the public swimming baths? Would a jury consider it ‘reasonable’ … A carpenter with a screwdriver, Yes; but a road runner with the same – No!
If you are carrying anything which could be construed as a weapon as you go to the gym or an event, you’d better have a damn good reason for having it with you, particularly if you happen to use it to flatten a would-be mugger or rapist on the way.
There are several factors for a successful self defence
1 You must have the TECHNICAL knowledge to defend yourself;
2 You must have the mental DETERMINATION to do so;
3 A Court must NOT be able to find you Guilty of an ASSAULT,
4 Nor of actually taking part in a FIGHT;
5 And your ‘victim’ must not be able to sue you for DAMAGES in respect of the severe injuries you gave him while defending against his assault.
It is easy to lose control and go overboard. You are legally allowed to defend yourself with ‘appropriate force’. The Law says so. But what is reasonable, appropriate force? If a yob tries to hit you with a brick, I suppose it would be reasonable to say “Look up at that Star!” as you kick him in the goolies. But it surely would not be reasonable for you then to smash his head in with his own brick?
But what if there were TEN other yobs about to join in? What then?
What do YOU think?
Self defence must STOP when the threat or attack ceases. And the mugger goes (or runs!) away. At that point you are probably legally secure.
But if you now chase after him and smash him on the head, things get awkward. You are aggrieved, enraged indeed, and want revenge. But you will have upgraded the confrontation into a FIGHT! If you enter a fight, the Law will have you, find you guilty and punish you. No question about that, no matter how good your (expensive, oh so expensive) private Counsel is.
This brings to mind the case of Tony Martin, the farmer found guilty of shooting dead an intruder – in the back. Martin (poor Tony!) was found guilty and sent to prison. Because the threat had been abated – the ‘victim’ was actually running away. There was no further danger to the farmer. But in his rage he fired. This manifestly was not a killing in self defence. But any of us could find ourselves in a similar situation. It is important that you realise this. What do you think?
And it is important that self defence instructors carefully explain these considerations to their students. As I’ve already said, It’s not only a case of learning what to do It’s also a matter of being actually morally and mentally able to do it. But secure in the knowledge that a jury will find that your actions were reasonable. And giving your ‘victim’ no chance whatsoever of suing you for huge financial damages.
Consider this scenario: running through the woods, a total stranger jumps out from the bushes and grabs you. With amazing self reliance and initiative you kick him in the groin… Down he goes, swearing.
Now, the Law says you must escape, run away fast from the danger which is no longer threatening you. Your adversary is rolling on the floor, swearing fiercely and clutching his groin. Out of action for at least five seconds.
But you are an athlete, you’ve never had such a physical confrontation in your life. What do you do? Legally, to stay out of jail you must beat a quick and hasty retreat. Remove yourself from the battle situation.
But if you stay and keep on hitting him, you are taking an active part in – A FIGHT! Jail looms large in your mind. So as a good law-abiding citizen, off you dash.
But you are shocked and confused, your legs won’t function properly. Your breath comes in gasps, in your panic you’ve lost your sense of direction – which way is safety? All is confusion and unreal!
Help! He’s getting up. Eyes watering with the effect of the kick to his privates and his hate for you! Faster than you, despite his injury, swearing horribly, he catches you, knocks you down and … Full stop!
Now here is the question. Here is the legal obscurity. Here is the jury’s problem. Here is YOUR desperate decision: while he was down and temporarily incapacitated, were you correct legally to run away. Or should you have seized the moment and waded in, jabbed your thumbs in his eyes, rabbit-chopped the back of his neck, then smashed his head in with that big stone over there? To put him away.
Well away. For Real!
What do you think? Quick, your answer. You’ve got five seconds to decide before he recovers enough to get up and ….
DO YOU RUN or …?
Is a problem!
Is YOUR problem.
What do YOU think?
John Roberts-James
http://www.articlesbase.com/sports-and-fitness-articles/self-defence-what-do-you-think-118333.html
How Cycling And Back Pain Are Related?
If it is an emphatic yes for swimming to cure the back pain, it is a strong no to the cycling, unfortunately. Millions of children and youth all over the world may not like this observation, but facts are facts.
Cycling done for long hours, contributes to many types of bodily imbalances, and may aggravate your back pain. However, cycling done for short durations may not do any major damage. It should be treated as just one of those exercises.
It is generally believed that cycling is one of the best methods to control and improve your overall fitness. While you do cycling, you get exercise to every part of your body. As you peddle, it is a good breathing exercise as well, provided you do it properly. But cycling has some disadvantages, especially if you have back pain. Cycling activity may not be possible at all, in case of acute back pain.
Cycling leads you to muscular imbalances. You may get chronic pain in certain parts of your body. It can never help you control your back pain.
Examine your riding posture on the cycle. Let’s start from the feet and then move up to the head.
Pedaling is a strenuous job, and it puts lots of stress on your calves. Tight calves mean your feet will flatten with lots of stress on the heel cord, knees and planter fascia. The major stress bearing muscles in cycling are the quadriceps.
Lots of cycling and the bent over cycling position is the cause of tightness in the quadriceps and the psoas (hip flexors). Now, you know the most damaging aspect of this position while cycling
Pelvis moves out of the optimal position and goes for a forward tilt. This is the beginning of the muscle imbalance. This is also the starting point of the strain of the lower back. There is lots of strain on the abdominals also. The hamstrings get overworked as you peddle forward, and they become tight.
The shoulders and the mid back have to bear the brunt. As you cycle your back is rounded and you with the back pain try to continue in a very difficult position. The shoulders are hiked up and pulled forward and you can well imagine the impact of it, if you continue cycling for longer duration.
The back pain will make you get down from the cycle automatically. If you still persist, neck tension and pain are guaranteed.
So, cycling can cause certain serious imbalances to your existing state of back pain. Why think of this exercise now? Postpone it for a future date, when you are completely cured form all sorts of back pain. Wait for some months!
Latest and better models of cycles are arriving in the market and they need your solid
‘back’ing!
Ashish Jain
http://www.articlesbase.com/advice-articles/how-cycling-and-back-pain-are-related-55414.html
Forex Trading – Back to School Forex Education
Foreign exchange trading could be a complex business to get into. The only way for any beginner to learn the ropes of forex trading is to go through intensive education and training. Quite heavy, so it seems. But, broken down in digestible chunks, you will soon be able to find your way around a successful forex trading business. There is a way to teach you the intricacies of forex trading in a simple and understandable way. Replicating the way you learned your ABCs and 123s, you will soon speak forex as if it is your second tongue. Soon, you will join the new breed of successful traders in the foreign exchange market.
Simply put, succeeding in forex trading rests on three things: making pips, keeping pips, and repeating the cycle. If you can master these three things, you are on your way to successful forex currency trading and forex options trading. To make things easy for you, you can break down your forex trading much like your early education was broken down. You move from one level to another once you have successfully completed the learning requirements of each level.
At the School of Pipsology, you learn the basics of forex from Pre-school, to elementary, to high school, to college, and then on to further more advanced studies. Graduating from each level will take you through learning milestones until you are finally able to identify trading opportunities, time the market, and close a trade. There are lots of important forex concepts to learn at the School of Pipsology if you want to be a successful forex trader. By the fifth grade level, you will already have learned how to do basic market analysis and read common chart indicators as Bollinger Bands, MACDs, Parabolic SARs, Stochastics, and RSIs. The best thing about it is that you can learn in simple terms and therefore at a faster pace.
Timothy Stevens
http://www.articlesbase.com/currency-trading-articles/forex-trading-back-to-school-forex-education-718116.html
The Importance Of Tire Pressure In Mountain Bikes
Tire pressure is a very important facet of riding any kind of bike, including mountain bikes. By learning how to set the tire pressure, you can give yourself more control and help to make the ride down the mountain smoother. If the tire pressure is too low, then you will find that it is much harder to cycle and it can increase the chance of a flat, too. Tire pressure that is too high can make your ride very bumpy and out of control, as well.
Tire pressure can vary from person to person, because it is dependent upon the personal preference of the bicycler, the tire’s condition, and the terrain that you will be riding on. The tire pressure can be easily modified simply by using a high quality pump on the tires. A tire pressure gauge is also an essential part of keeping your tires at the optimum pressure.
The manufacturer of the tire will have a recommended tire pressure for your particular tires and this is where you can start. You can then adjust the tire pressure as needed from there. It is best to use the same tire pressure gauge and pump when you check your tires, because you may get different readings depending upon the tire pressure gauge that you choose.
A good rule of thumb is to start with a higher tire pressure for your bike. This means that you want to be around 40-50 psi (3-3.5 bar), and then lower the tire pressure a little at a time to find which tire pressure is best for your particular bike, terrain, and yourself. If you are a little heavier, then you will want to use a higher tire pressure for sure.
Taking a test bike ride is the best way to check the tire pressure. You will want to notice how the tire behaves, how it rides on the terrain, how it slides down the mountain, and how it hooks in the corners. If you have too much tire pressure, then drop it in increments of 5 psi in both tires. If the bike gains grip and is more stable at this tire pressure, then you will want to keep it at this standard pressure. If not, then you will continue dropping the tire pressure in small increments and redoing the test until your bike rides the way you want and need it to.
If you want to determine the lowest possible tire pressure, then gradually decrease the tire pressure until you see how it feels when you ride on almost flat tires. This will help you to learn how it feels so that you can keep your tubes from getting damaged.
If your mountain bike tires are tubeless, then you will want to stay with a lower tire pressure. The advised tire pressure for tubeless tires is between 30 and 40 psi. This is because tubeless tires experience fewer pinch flats and even rim contact occasionally is okay. This is why you can ride on tires with a much lower tire pressure than normal. If the tire pressure is too low, you will find that if you are cornering hard that the tire will roll under the rim.
Another thing that you need to be on the lookout for is rolling resistance. The increased rolling resistance will take more effort, but it will offer you greater control and better traction to allow you to climb easier. For racers who race cross-country, they would rather have a more efficient bike versus greater control, so you have to take into consideration what kind of biking that you will be doing.
Using your hand to squeeze the tire will help you determine what the right tire pressure feels like so that you do not have to rely so much on the tire pressure gauge.
Alastair Hamilton
http://www.articlesbase.com/sports-and-fitness-articles/the-importance-of-tire-pressure-in-mountain-bikes-101015.html
Introduction to Plc and Scada
Introduction to PLC’s
Programmable Logic Controllers
Bedford Associates, founded by Richard Morley introduced the first Programmable Logic Controller in 1968. This PLC was known as the Modular Digital Controller from which the MODICON company derived its name. The History of the PLC as told to Howard Hendricks by Dick Morley provides an interesting insight into the early development of the PLC.
Schnieder Quantum PLC
Programmable Logic Controllers were developed to provide a replacement for large relay based control panels. These systems were inflexible requiring major rewiring or replacement whenever the control sequence was to be changed.
The development of the micro processor from the mid 1970’s have allowed Programmable Logic Controllers to take on more complex tasks and larger functions as the speed of the processor increased.
Ladder Logic
PLC had to be maintainable by technicians and electrical personnel. To support this the programming language of Ladder Logic was developed. Ladder Logic is based on the relay and contact symbols technicians were used to through wiring diagrams of electrical control panels.
Until recently there has been no formal programming standard for PLC’s. The introduction of the IEC 61131 Standard in 1998 provides a more formal approach to coding. PLC Manufacturers have so far been slow on the uptake of the standard with partial implementation. The SearchEng articleIEC 61131-3, a Standard for PLC Software by R.W. Lewis provides an introduction to the standard.
The documentation for early PLC Programs was either non existent or very poor, just providing simple addressing and basic comments, making large programs difficult to follow. This has been greatly improved with the development of PLC Programming Packages.
SCADA and HMI
The early programmable logic controllers interfaced with the operator in much the same way as the relay control panel, via push-buttons and switches for control and lamps for indication.
The introduction of the Personal Computer (PC) in the 1980’s allowed for the development of a computer based interface to the operator, these where initially via simple Supervisory Control and Data Acquisition (SCADA) systems and more recently via Dedicated Operator Control Panels, known as Human Machine Interfaces (HMI).
The History of the PLC
as told to Howard Hendricks by Dick Morley
The following are some fables associated with the first ten years of the programmable controller business. These Fables may or may not have a basis of truth, but in general, they are the best that my Alzheimer-plagued memory can do at the moment. As has been often in other articles and reports, the startup of Modicon and the programmable controller industry as a whole is well documented. The programmable controller was detailed on New Year’s Day, 1968, and from hence till now, a slow steady growth has allowed the manufacturing and process control industries to take advantage of applications-oriented software.
The early days however, were not as straightforward nor as simple. We had some real problems in the early days of convincing people that a box of software, albeit cased in cast iron, could do the same thing as 50 feet of cabinets, associated relays and wiring. The process was indeed difficult, and deserves some of the stories that I hope the reader will be regaled with as he proceeds onward through the tortuous swamp of my mind.
One of my earliest recommendations was that the programmable controller, according to my own system architecture specification, did not need to go fast because I felt as though speed was not a criteria because it would go as fast as we needed it to. The initial machine, which was never delivered, only had 125 words of memory, and speed was not a criteria as mentioned earlier. You can imagine what happened! First, we immediately ran out of memory, and second, the machine was much too slow to perform any function anywhere near the relay response time. Relay response times exist on the order of 1/60th of a second, and the topology formed by many cabinets full of relays transformed to code is significantly more than 125 words. We expanded the memory to 1K and thence to 4K. At 4K, it stood the test of time for quite a while. Initially, marketing and memory sizes were sold in 1K, 2K, 3K, (?) and 4K. the 3K was obviously the 4K version with constrained address so that field expansion to 4K could easily be done.
The question of speed, in part, was part of the early designs. No interrupts were necessary because the external signal conditions were directly written onto memory without any supervisory requirements or “operating system of the conventional type. This allowed the processor to pay attention to solving logic rather than housekeeping the I/O. As a result, of course, the processor had to have significantly more processing power than normally associated with this size computer; and secondly, the system had to be made to run fast.
We increased the memory size, as mentioned above, but to get it to run fast, we had to break up the machine into three distinct components. Initially, the programmable controller was conceived of a processor board and a memory, and that the algorithmic and logical manipulation would be done in software. This approach was painfully slow, both on the generic “store bought computers, and other items.
We did, however, manage to substantially speed up the machine by making a third major component. This was called the logic solver. A logic solver board solved the dominant algorithms associated with solving ladder logic without the intervention and classical software approach of general-purpose processing. This meant that we ended up with three boards; memory, logic solver and processor. This single step allowed us to get the speed we needed in this application-specific computer to solve the perceptually simple problem of several cabinets full of relay wiring.
We had also assumed a modular approach to the programmable controller. In act, the name Modicon means MOdular DIgital CONtroller. The modularity, however, was soon abandoned because, as everyone knows, open architectures are no good. We instead had the marketing premise that a large footprint would contain within it the sets of problems we wished to solve. This meant that a buyer of programmable controllers could buy large numbers of the same units, and the software and hardware would be identical across a broad spectrum of applications in his factory. Service, maintenance and total life cost would be substantially lower than the perceived lower cost of an open architecture and modular expansion. Although at first, a supporter of the open architecture modular expansion, I soon became convinced by the marketplace, but this was folly.
We took one of our early units which was aimed at the machine tool industry because of my Bedford Associates consulting background, up to one of the early requesters of this equipment. This particular early requester was Byrant Chuck and Grinder in Springfield, Vermont. We took the machine up there, and it was heavy. This was the 084. The 084 was in the trunk of my old Pontiac, and since we needed help carrying it in, requested some of the people at Bryant to help us. We went out and opened the hood, and the first comment made by an outside viewer of the programmable controller said, “Thank God it,s not another pastel colored piece of sheet metal.
We can hypothesize from this particular comment that the ruggedness of the visual design was pleasing to him, and being human (as opposed to Martian), assumed that this same attitude went deep inside the construction of the machine in both the hardware and software. Indeed, this was the case, and the machine as a result, was built rugged, had no ON/OFF switch, had no fans, did not make any noise and had no wear out system.
To reminisce for a moment—in selecting the cores for the first memories, which in itself was a revolutionary step, we selected these cores and we applied Shannon,s Law. Shannon,s Law assumes that the signal-to-noise ratio is what makes signals good or bad. There are several ways to get the power from the signal-to-noise ratio; one is to code heavily, be triply redundant, and use lots and lots of error checking. There is another way, which is perfectly compatible with theory, which is to use lots of signal power in another domain. A nice switch, a car battery and a D-rated light bulb will work fairly well over a long time period.
Therefore, what we did was rather than going error checking, triply redundant and stuff, we got, and searched for and found high energy, large ferrite core memories that had lots on energy per bit. We still make the same assumption today. The energy per bit is extremely important—as Shannon,s theory said in his most famous 1948 paper, that the signal noise to power noise is what gives you transmission. the way we got signal power was to increase the energy per bit. This we felt was far more important than getting the energy per bit increased by means of doubly transmitting it. But I digress. Bryant Chuck and Grinder put it in, and liked the equipment so much that they never bought one. They in turn thought it was a good idea, and as many did at that time, tried to evolve their own.
One of our first major customers, however, was Landis in Landis, PA. We flew the equipment down in a private aircraft, and with apprehension because we were late (as usual), brought the equipment into Landis. In doing so, we tripped over the threshold. The equipment went KA-RASH onto the floor! Without much chagrin, we picked the equipment up, trundled it in. hooked it up, and low and behold, it worked quite well.
Now, Landis was pleased and surprised. They were pleased because it worked, but they were most pleasantly surprised—not because the equipment worked—but because the guys from Modicon fully expected the equipment to work in spite of it being dropped. In other words, the people from Modicon weren,t nervous about the fact that it fell on the floor over the threshold.
Landis subsequently took and wrapped welding coils of wire around the machine to induce electro-magnetic noise to see if they could make it fail. We had them there! We used to test the programmable controllers with a Teslar coil that struck a quarter inch to half-inch arch anywhere on the system, and the programmable controller still had to continue to run. There was significant strangeness with respect to the programmable controller. For example, it had no ON/OFF switch. It had no means to load software. It had no fans. It ran cool. It could survive bad, physical and thermal environments. It was not computer industry standard. There were many things that were most difficult in the acceptance of the programmable controller, and early acceptance was most difficult indeed.
Our sales in the first four years were abysmal. Early innovators such as Landers and General Motors were, of course, heroes to our eyes, but they would buy small numbers of units and then test them in the field before they committed themselves later on. We had one customer in the utilities business that took them approximately six to seven years to make a decision to but the first one.
We never really sold any programmable controllers into the intended market which was machine tool control such as lathes, grinders and stuff, but we did, as luck would have it, stumble across the transfer line market which was and still is the mainstay, long-term market for the application of programmable controllers. Discreet parts manufacturing in an automatic environment, i.e., mass production, continues to be, and probably will be for the future, the mainstay of the programmable controller industry.
Some of the more interesting stories center around the personalities and experiences as opposed to the programmable controller. Modicon,s third president (or fourth, if you count my two-week stint) was Don Kramer. When Don Kramer was chosen as president, we decided to go out and celebrate at the Lanum Club in Andover. At the time, we felt we should celebrate over both martinis and food. As we were leaving the shop for the Lanum Club, Don made the aside comment that “the place is dingy and needs a paint job. As we were leaving, I mentioned to Don that as president you have to change what you say, and not be very open—you have to be a little careful about what you say because employees, customers, and boards of directors tend to take what you say as truth. Rather than listen to the meaning, they listen to the literal statements, and one must be careful. We went over to the Lanum Club and had a nice glowing two hours of discussion, food, and drink. Coming back, as we entered the Modicon lobby, we noticed that there was scaffolding about and people were painting. We went over and asked Lou as to why these people are painting since, at the time, we don,t have any money. Who ordered this paint job? And Lou looked Don Kramer straight in the eye, and said, “Why you did, Mr. Kramer. Nuff said.
As has been mentioned many times, your author, that,s me—Dick Morley—is supposed to be the inventor of the programmable controller. This is at best, partially true. The thing that made the Modicon company and the programmable controller really take off was not the 084, but the 184. The 184 was done in design cycle by Michael Greenberg, one of the best engineers I have ever met. He, and Lee Rousseau, president and marketeer, came up with a specification and a design that revolutionized the automation business. they built the 184 over the objections of yours truly. I was a purist and felt that all those bells and whistles and stuff weren,t “pure, and somehow they were contaminating my “glorious design, Dead wrong again, Morley! they were specifically right on! the 184 was a walloping success, and it—not the 084, not the invention of the programmable controller—but a product designed to meet the needs of the marketplace and the customer, called the 184, took off and made Modicon and the programmable controller the company and industry it is today. My compliments to the two chefs—Lee Rousseau and Mike Greenberg.
The issue of quality in programmable controllers is a story that is normally taken for granted. The gentle reader must remember that our engineering people came from the computer industry where reliability in those days was a phantom—a phantom of design, a phantom of cost. People felt that reliability was something other people did, and that if we only could deliver faster computers, even if they didn,t work, everything would be fine.
When the programmable controller was designed, it was designed in to be reliable. We used lots of energy per information bit by utilizing D-rated components, large memory ferrite cores, relatively stable and large etchings on printed circuit boards, totally enclosed systems and conductive cooling. No fans were used, and outside air was not allowed to enter the system for fear of contamination and corrosion. Mentally, we had imagined the programmable controller being underneath a truck, in the open, and being driven around—driven around in Texas, driven around in Alaska. Under those circumstances, we anted it to survive. The other requirement was that it stood on a pole helping run an utility or a microwave station which was not climate controlled, and not serviced at all. Under those circumstances, would it work for the years that it was intended to be? Could it be walled in? Could it be bolted in a system that was expected to last 20 years?
The humorous side of this is though we did all those designs and very carefully tried to make this system as intrinsically reliable as we could, not by redundancy, but by building well. In other words, it was designed to be built, it was designed to be designed, and it was designed to be reliable. We, however, as engineers, didn,t understand the accountants and manufacturing. those two have their grail, shipments by the end of the month. As far as we could ascertain at the time, shipments were made independent of quality and independent of whether or not the system ran.
In the early days of the programmable controller and Modicon, even though I wasn,t a direct employee and an owner, I would give out my home phone number to many of our critical customers so that if they had a problem, they could call me directly. Several calls indicated that when we shipped near the end of the month, let’s say October 34th, that the equipment would not run; and secondly, when they opened the box and took the machine apart, cards were missing, bolts were on the bottom of the cabinetry, and some of the cards were not fully inserted. In other words, to make the end of the month was much more important than to deliver equipment that ran. to put it mildly, we were pissed! How do we as engineers maintain quality without continual surveillance which is most difficult for the design and entrepreneurial mind set. What we did was specify and design “blue boxes. These were cabinetries that the system had to operate in and run continuously for a minimum of 24 hours, under load, and under varying conditions. The box was built out of plywood, but its primary intention was to heat cycle the programmable controller under various input/output loads. We also ran, as a specification, that a Tesla coil was to be used on the programmable controller, and that vibration and thumping with a hammer (rubber) would be part of the specification.
This may seem unscientific to many of you, but let us assume that you try to get your equipment to run while somebody purposely tries to destroy it with a rubber hammer or spark coil that he can put anywhere on the system. Remember, your intention is to make the processor stop. That combination significantly depressed those monthly shipments during the first period. As a result of that, however, the message got through. Not only did we build ovens and tests, and pay attention to heat and spark and RF emissions, we would run the system continuously even in the shipping crate to get the maximum number of pre-custom hours we could. It was important to us that we found the mistakes and not the customer and his secondary customer.
The language itself, ladder lister, bears some discussion. This particular language was not the invention of Modicon. We hypothesize that the language is very old, and originated in Germany to describe relay circuitry. If one looks at ladder lister, it has been our technical community for so long, we somehow think those little symboligies actually look like relays. In fact, it,s a mnemonic form of rule-based language, very modern and very high level, but designed in a Darwinian fashion over a period of many decades.
The ladder logic construct, “If… Then… is a very powerful construct used today in expert systems and other rule-based languages. The symbology, allowing normally open and normally closed situations as well as parallel and serial representation, was used for many decades before the invention of the programmable controller. I have worked on machines where the number of C-size and D-size prints were hung in special racks, and would be up to three feet thick worth of documentation on those drawing sets.
The name ladder comes from the fact that on the right-hand of the drawing is one power rail and the left-hand side is the other power rail; and in between in a horizontal fashion, is the statement or sequential connection of logical elements which we call relays or relay logic. The initial 084 had only logic in its functionality, and as a result, was marginal. In other words, all we did was replace relays rather than enhance the functionality by a factor of ten which is the entrepreneurial rule. Immediately, of course, based on customer response and our own frustrations, we put thing in the ladder listing language such as addition, multiplication, subtraction, and other functionalities that went far beyond relay capability and entered the realm of mathematics and set theory. This was still not sufficient, however, and we needed some way to make a “call to a “subroutine using ladder lister symbology and representation.
A software engineer, Chuck Schelberg, and myself were in the conference room one day trying to ascertain how we could make a generic call to functionalities that far exceeded the relay symbology and representation, and came up with the “DX function. This function was a block function that would be an element on the ladder logic representation that could perform many functionalities including arrays, motor drive functions, servo functions, extended mathematical functions, PID loops, ad nauseam. We felt there would be an occasional representation and use of these functionalities, and that not much had to be done to the programmable controller other than to modify the software. Wrong again!
The first customer that took delivery of a programmable controller utilizing the DX function, had a capability to be predictable and operate in real time. The RUN light went out, and the time to execute a scan or complete transformation of the ladder logic went far beyond the time allowable. Every single line had a DX function on it. Again we learned that when you enhance functionality, people use it all. I have never designed a computer that had too much memory. I,ve only designed computers that have too little memory. The same thing applies to any other functionality. Conventional wisdom seems to think that price/performance depends on only one thing—price—when, in fact, my experience has been that the customer cares little about price.
This price/performance tirade being over, one of the lessons we learned is that the customer wants functionality over the entire life cycle cost installation of the job. the customer also wants ease of installation, to have some fun, and to be proud of the work he does. After he,s finished, he never wants to come back.. The equipment should work as installed and as based. At one time, the programmable controller meantime before failure in the field was 50,000 hours. This is far in excess of almost any other type of electronic or control equipment.
The concept of languages and high-level languages is important. The programmable controller, as it evolved, began to request more and more power, and more and more memory. The memories continually went up as well as power. It is estimated that at one time, in the mid-1970s, that the programmable controller had the equivalent of two MIPS processor and 128 kilobytes of memory, which at that time was a significantly powered minicomputer capability. Why? High-level languages require power to run them. If we take the equivalent of the ladder lister statement “If… Then…, the high-level language as represented here, requires a substantial amount of interpretive compiler, if you will, generation of underlying code. In other words, this statement spawns significant underlying code that must be run quickly, reliably, and contain within it, all aspects of resource allocation and operations resource. The higher level the language, the more powerful the processor apparently has to be in order to run the language. Ladder lister is a high-level rule-based language which, until now, we haven,t talked much about in these terms. Our customers treated the programmable controller as a box of relays, and well they should. Language theory is neither necessary not desirable for most of the customers to know. The customers, instead, understand their problem, and are indeed much smarter than the design engineers because the dimensions of their problem far exceed the relatively simple problem of designing a computer software system and language. Ladder lister requires high performance which is one of the reasons it has difficulty running on the personal computer even of today
INTRODUCTION TO SCADA
SCADA is the abbreviation for Supervisory Control And Data Acquisition. It generally refers to an industrial control system: a computer system monitoring and controlling a process. The process can be industrial, infrastructure or facility based as described below:
Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, and large communication systems.
Facility processes occur both in public facilities and private ones, including buildings, airports, ships, and space stations. They monitor and control HVAC, access, and energy consumption.
A SCADA System usually consists of the following subsystems:
A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator monitors and controls the process.
A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process
Remote Terminal Units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.
Communication infrastructure connecting the supervisory system to the Remote Terminals Units
There is, in several industries, considerable confusion over the differences between SCADA systems and Distributed control systems (DCS). Generally speaking, a SCADA system usually refers to a system that coordinates, but does not control processes in real time. The discussion on real-time control is muddied somewhat by newer telecommunications technology, enabling reliable, low latency, high speed communications over wide areas. Most differences between SCADA and Distributed control system DCS are culturally determined and can usually be ignored. As communication infrastructures with higher capacity become available, the difference between SCADA and DCS will fade.
Systems concepts
The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything between an industrial plant and a country). Most control actions are performed automatically by remote terminals units (”RTUs”) or by programmable logic controllers (”PLCs”). Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.
Data acquistion begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required. Data is then compiled and formatted in such a way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls. Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing.
SCADA systems typically implement a distributed database, commonly referred to as a tag database, which contains data elements called tags or points. A point represents a single input or output value monitored or controlled by the system. Points can be either “hard” or “soft”. A hard point represents an actual input or output within the system, while a soft point results from logic and math operations applied to other points. (Most implementations conceptually remove the distinction by making every property a “soft” point expression, which may, in the simplest case, equal a single hard point.) Points are normally stored as value-timestamp pairs: a value, and the timestamp when it was recorded or calculated. A series of value-timestamp pairs gives the history of that point. It’s also common to store additional metadata with tags, such as the path to a field device or PLC register, design time comments, and alarm information.
Human Machine Interface
A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.
An HMI is usually linked to the SCADA system’s databases and software programs, to provide trending, diagnostic data, and management information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides.
The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled. For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.
The HMI package for the SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.
An important part of most SCADA implementations are alarms. An alarm is a digital status point that has either the value NORMAL or ALARM. Alarms can be created in such a way that when their requirements are met, they are activated. An example of an alarm is the “fuel tank empty” light in a car. The SCADA operator’s attention is drawn to the part of the system requiring attention by the alarm. Emails and text messages are often sent along with an alarm activation alerting managers along with the SCADA operator.
Hardware solutions
SCADA solutions often have Distributed Control System (DCS) components. Use of “smart” RTUs or PLCs, which are capable of autonomously executing simple logic processes without involving the master computer, is increasing. A functional block programming language, IEC 61131-3, is frequently used to create programs which run on these RTUs and PLCs. Unlike a procedural language such as the C programming language or FORTRAN, IEC 61131-3 has minimal training requirements by virtue of resembling historic physical control arrays. This allows SCADA system engineers to perform both the design and implementation of a program to be executed on an RTU or PLC. Since about 1998, virtually all major PLC manufacturers have offered integrated HMI/SCADA systems, many of them using open and non-proprietary communications protocols. Numerous specialized third-party HMI/SCADA packages, offering built-in compatibility with most major PLCs, have also entered the market, allowing mechanical engineers, electrical engineers and technicians to configure HMIs themselves, without the need for a custom-made program written by a software developer.
Remote Terminal Unit (RTU)
The RTU connects to physical equipment. Typically, an RTU converts the electrical signals from the equipment to digital values such as the open/closed status from a switch or a valve, or measurements such as pressure, flow, voltage or current. By converting digital setpoints to electrical signals and sending these electrical signals out to equipment the RTU can control equipment, such as opening or closing a switch or a valve, or setting the speed of a pump.
Quality SCADA RTUs have these characteristics:
Data Networking capability
Data Reliability
Data Security.
Supervisory Station
The term “Supervisory Station” refers to the servers and software responsible for communicating with the field equipment (RTUs, PLCs, etc), and then to the HMI software running on workstations in the control room, or elsewhere. In smaller SCADA systems, the master station may be composed of a single PC. In larger SCADA systems, the master station may include multiple servers, distributed software applications, and disaster recovery sites. To increase the integrity of the system the multiple servers will often be configured in a dual-redundant or hot-standby formation providing continuous control and monitoring in the event of a server failure.
Initially, more “open” platforms such as Linux were not as widely used due to the highly dynamic development environment and because a SCADA customer that was able to afford the field hardware and devices to be controlled could usually also purchase UNIX or OpenVMS licenses. Today, all major operating systems are used for both master station servers and HMI workstations.
Operational philosophy
For some installations, the costs that would result from the control system failing is extremely high. Possibly even lives could be lost. Hardware for some SCADA systems is ruggedized to withstand temperature, vibration, and voltage extremes, but in most critical installations reliability is enhanced by having redundant hardware and communications channels, up to the point of having multiple fully equipped control centres. A failing part can be quickly identified and its functionality automatically taken over by backup hardware. A failed part can often be replaced without interrupting the process. The reliability of such systems can be calculated statistically and is stated as the mean time to failure, which is a variant of mean time between failures. The calculated mean time to failure of such high reliability systems can be on the order of centuries.
Communication infrastructure and methods
SCADA systems have traditionally used combinations of radio and direct serial or modem connections to meet communication requirements, although Ethernet and IP over SONET / SDH is also frequently used at large sites such as railways and power stations. The remote management or monitoring function of a SCADA system is often referred to as telemetry.
This has also come under threat with some customers wanting SCADA data to travel over their pre-established corporate networks or to share the network with other applications. The legacy of the early low-bandwidth protocols remains, though. SCADA protocols are designed to be very compact and many are designed to send information to the master station only when the master station polls the RTU. Typical legacy SCADA protocols include Modbus RTU, RP-570, Profibus and Conitel. These communication protocols are all SCADA-vendor specific but are widely adopted and used. Standard protocols are IEC 60870-5-101 or 104, IEC 61850 and DNP3. These communication protocols are standardized and recognized by all major SCADA vendors. Many of these protocols now contain extensions to operate over TCP/IP. It is good security engineering practice to avoid connecting SCADA systems to the Internet so the attack surface is reduced.
RTUs and other automatic controller devices were being developed before the advent of industry wide standards for interoperability. The result is that developers and their management created a multitude of control protocols. Among the larger vendors, there was also the incentive to create their own protocol to “lock in” their customer base. A list of automation protocols is being compiled here.
Recently, OLE for Process Control (OPC) has become a widely accepted solution for intercommunicating different hardware and software, allowing communication even between devices originally not intended to be part of an industrial network.
Trends in SCADA
There is a trend for PLC and HMI/SCADA software to be more “mix-and-match”. In the mid 1990s, the typical DAQ I/O manufacturer supplied equipment that communicated using proprietary protocols over a suitable-distance carrier like RS-485. End users who invested in a particular vendor’s hardware solution often found themselves restricted to a limited choice of equipment when requirements changed (e.g. system expansions or performance improvement). To mitigate such problems, open communication protocols such as IEC870-5-101/104 and DNP 3.0 (serial and over IP) became increasingly popular among SCADA equipment manufacturers and solution providers alike. Open architecture SCADA systems enabled users to mix-and-match products from different vendors to develop solutions that were better than those that could be achieved when restricted to a single vendor’s product offering.
Towards the late 1990s, the shift towards open communications continued with individual I/O manufacturers as well, who adopted open message structures such as Modbus RTU and Modbus ASCII (originally both developed by Modicon) over RS-485. By 2000, most I/O makers offered completely open interfacing such as Modbus TCP over Ethernet and IP.
SCADA systems are coming in line with standard networking technologies. Ethernet and TCP/IP based protocols are replacing the older proprietary standards. Although certain characteristics of frame-based network communication technology (determinism, synchronization, protocol selection, environment suitability) have restricted the adoption of Ethernet in a few specialized applications, the vast majority of markets have accepted Ethernet networks for HMI/SCADA.
“Next generation” protocols such as OPC-UA, Wonderware’s SuiteLink, GE Fanuc’s Proficy and Rockwell Automation’s FactoryTalk, take advantage of XML, web services and other modern web technologies, making them more easily IT supportable.
With the emergence of software as a service in the broader software industry, a few vendors have begun offering application specific SCADA systems hosted on remote platforms over the Internet, for example, PumpView by MultiTrode. This removes the need to install and commission systems at the end-user’s facility and takes advantage of security features already available in Internet technology, VPNs and SSL. Some concerns include security, Internet connection reliability, and latency.
SCADA systems are becoming increasingly ubiquitous. Thin clients, web portals, and web based products are gaining popularity with most major vendors. The increased convenience of end users viewing their processes remotely introduces security considerations.
Security issues
The move from proprietary technologies to more standardized and open solutions together with the increased number of connections between SCADA systems and office networks and the Internet has made them more vulnerable to attacks. Consequently, the security of SCADA-based systems has come into question as they are increasingly seen as extremely vulnerable to cyberwarfare/cyberterrorism attacks.
In particular, security researchers are concerned about:
the lack of concern about security and authentication in the design, deployment and operation of existing SCADA networks
the mistaken belief that SCADA systems have the benefit of security through obscurity through the use of specialized protocols and proprietary interfaces
the mistaken belief that SCADA networks are secure because they are purportedly physically secured
the mistaken belief that SCADA networks are secure because they are supposedly disconnected from the Internet
Because of the mission-critical nature of a large number of SCADA systems, such attacks could, in a worst case scenario, cause massive financial losses through loss of data or actual physical destruction, misuse or theft, even loss of life, either directly or indirectly. Whether such concerns will cause a move away from the use of existing SCADA systems for mission-critical applications towards more secure architectures and configurations remains to be seen, given that at least some influential people in corporate and governmental circles believe that the benefits and lower initial costs of SCADA based systems still outweigh potential costs and risks] Recently, multiple security vendors, such as Byres Security, Inc., Industrial Defender Inc., Check Point and Innominate, and N-Dimension Solutions have begun to address these risks by developing lines of specialized industrial firewall and VPN solutions for TCP/IP-based SCADA networks. The problem according to Eric Byres, CEO of Byres Security, is that “while many infrastructure organizations are doing good work, others are falling behind. When you have this diversity of effort, you are only as effective as your weakest link.
Also, the ISA Security Compliance Institute (ISCI) is emerging to formalize SCADA security testing starting as soon as 2009. ISCI is conceptually similar to private testing and certification that has been performed by vendors since 2007, such as the Achilles certification program from Wurldtech Security Technologies, Inc. and MUSIC certification from Mu Security, Inc. Eventually, standards being defined by ISA SP99 WG4 will supersede these initial industry consortia efforts, but probably not before 2011.
N.Sankari
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