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TEMPERATURE CONTROL APPLICATION GUIDES

TEMPERATURE CONTROL APPLICATION GUIDES

Eurotherm Terms
  • Cutback -- Built-in overshoot inhibition software
  • Holdback -- for ramp/dwell programming controllers
  • Instant Accuracy™ (summary)
  • Instant Accuracy™ A Technical Definition
  • PDSIO™ -- Pulse Density Signaling I/O -- a summary.
  • PID (Proportional, Intregal, Derivative) control and tuning techniques (9 pages).
  • Power Feedback
  • Series 2000 scroll parameters listing and definitions



  • Articles on Temperature and Power Control Technology in Industry and Research
    by Arthur Holland, Holland Technical Skills, Oakville ON Canada
     
    Who can benefit from these articles?
    1. People in the broad field of process heating, who are time limited and have to deal in short order with various control problems - among their many other jobs.
    2. Instrument and Electrical technicians under pressure to bring a process back on line.
    3. The overloaded customer-support desks of control equipment suppliers. The caller is often unfamiliar with this technology and its vocabulary; so a look at relevant article from this list can often avoid a long dialog with the help desk.

      1 A look at 4 - 20 Milliamp Signals
    4 - 20 Ma; the analog signal of choice. Its characteristics, its use to represent process variables, control, retransmission, transmitter outputs, set point, position, and feedback signals. Signal converter inputs and outputs (38KB)
      2 Buying a Temperature Controller? Understand the Specification Before you Order
    A thorough look at the many ingenious features of the discrete temperature controller. How it has adapted itself to fit every known heat process and application. This tells you how to be an informed user and how to select the best buy. (210KB)
      3 Calibrating and Testing Control Components on Your Heat Process. What, when and how should I calibrate?
    All about best calibration practices, features of calibrators for linear and the many non-linear signals from transducers signal conditioners and temperature sensors. Calibration of controllers recorders and indicators. (64K)
      4 Cascade Control. Handle Processes that Challenge Regular PID Control
    Control sluggish processes that are too much for normal PID control. How to tighten them up using cascade control. Example. (53K)
      5 Compare your Energy Prices Easier Said than Done
    How to cut through the jungle of different energy price offers that are designed to confuse and defeat your right to make the best deal. (26KB)
      6 Understand your Heat Process Problems and How PID Control Deals with Them
    Understand what makes a process hard or easy to control. How PID is defined. Look at these and other control refinements and how they are put to work. (300KB)
      7 Is Electrical Interference Crippling your Control System? Understand it and You can Defeat It
    Look at the various mechanisms of electromagnetic interference, how they hurt your process and how to fight them. (172KB)
      8 Wasting Energy: How does your Plant Rate?
    A case history. How a power-hungry extruder was analyzed and put to work on a lean diet. (22KB)
      9 Engineering Units in the Process Heating Workplace; How Handy are they to Visualize and Use?
    How to get your mind round engineering units in the process heating workplace.. Here's how they look and feel. Free yourself from the handcuffs of those quaint antique units; work easier and faster. (72KB)
      10 Where Feedback Benefits your Process
    How feedback works for you when controlling your process. Makes circuits stable, robust and linear. Makes your actuator go exactly where the signal told it in the face of friction and line pressure. Gives your heater the exact power the controller demanded. (180KB)
      11 Feedforward on Temperature Control Systems. Fast Compensation for Disturbances
    Feedforward watches your process and warns the controller to immediately deliver a measured response to changes. This leaves the sensor and overall control loop with much less work to do in chasing and correcting deviations. An example. (185KB)
      12 Final Control Elements. The Devices that Modulate Process Heat
    They provide the muscle for your process. Magnetic and solid state contactors, SCRs, Electric motor and electropneumatic actuators for valves and dampers. Motor speed controllers. (159KB)
      13 How Ground Loops Harm your System
    When you see malfunctions or gross measurement errors look at the components of your system and check for misconnections or components that share a common line or ground. (83KB)
      14 How Instrumentation Can Reduce Hazards to People and Plant
    An account of an expensive refinery accident and the many protective features and techniques available on modern controllers. (30KB)
      15 Heating Billets ready for Diecasting
    Choose the coil arrangement, power and frequency for induction heating an aluminum billet (22KB)
      16 Your Heater Material and Design Dictate how you Control it
    Look at the characteristics of four common heater element materials and consider how best to control them (84KB)
      17 Troubleshooting Temperature Control Equipment
    Tool and tips for finding and clearing process problems (221KB)
      18 Master Slave Temperature Control, Three Ways to Achieve it.
    An example of a two-platen press where the second platen is required to track the temperature of the first platen. The principles here are applicable to a great variety of processes. (98KB)
      19 Understand the Instrumentation on your Heat Process
    A description of the features of the many installed instruments on your process and a discussion of those of a different class: the test and trouble-shooting instruments you will need to start up and maintain the process (66KB)
      20 Non-contact Temperature Sensing
    arious ways to sense the temperature of the untouchable using thermocouples, RTDs and optical thermometers. (66KB)
      21 Power Factor. Two Myths and some Words of Comfort
    A review of the different aspects of power factor; how low power factors can cost you money. How to define it in SCR power control. (177KB)
      22 Protective Devices for Electrical Control Equipment
    All about Fuses, Circuit breakers, SCR Chop off Circuits, Crowbars, Thermostats over-temperature shut-offs and fusable links (184KB)
      23 Ramp and Soak Applications
    A case history. the buckling oven. Techniques and versatile features of temperature programming systems. (71KB)
      24 Ratio Control. Some of its Applications and Imperfections
    How to make two process variables keep the same ratio regardless of how wild and variable they are. (110KB)
      25 A Book on Electroheat by A.C. Metaxas: Worth a Look
    For anyone interested in the many ways of delivering electroheat this book is well worth a study. It is based on courses on Electroheat given in the Engineering Department of Cambridge University. Here Metaxas combines mathematical treatment of the principles of electroheat with descriptions and sketches of a wide variety of real industrial applications (23KB)
      26 SCR Control of Electric Heaters
    The many ways that SCRs are used to control and manipulate electric power in the face of difficult heaters and unstable power sources. (109KB)
      27 Silicon Controlled Rectifiers and Transformers in Power Control.
    How transformers extend the capabilities of SCRs. Examples of single-phase, three-phase, wye and delta connections, Scott T connections for three to two or to one phase (292KB)
      28 You want good Control? Check the Location and Construction of your Temperature Sensor
    The best controller can be defeated by a badly designed or located temperature sensor. Here are some examples of these problems followed by some solutions and precautions. (43KB)
      29 Signal Conditioners. The little hidden boxes that manipulate your process signals
    Modifying your process? Have some jobs that cannot be performed by the regular control system? You need an extra device of some kind. Look in your catalogue for small hockey-puck shaped or DIN rail mounted components. These are Signal conditioners - essential items in the inventor's tool kit. (56KB)
      30 Smart Field-mounted Control Components They obey your commands and tell you how they're doing.
    Those dumb and obedient field devices - control valves, power control devices, temperature sensors, signal converters, transducers and motor drives have for some time been evolving smart features. This has opened up process diagnostics, aided preventive maintenance and plant up time and don't forget - greatly simplified plant wiring. (115KB)
      31 Traps and Color Confusion in Thermocouple Wiring.
    Multiple so-called national standards for colour codes of thermocouple extension cables have been responsible for many cases of process instabilities and upsets. Here is a costly example. Internationally agreed standards, in use since 1989 are still rare in N America. (131KB)
      32 Thermocouples: Eight established types to choose from. What type do I need and what should be abandoned?
    So your application calls for a thermocouple. This is just the beginning - you are faced with too many choices. Here is a brief account of which one fits which application and which ones can be struck from the list for ever. (68KB)
      33 Trouble shooting on Extrusion Temperature Control Equipment
    This is a big topic. It deals first with how to know your machine, how it behaves well and how it can go wrong. The control techniques described here represent the results of continuous development and refinement as control equipment manufacturers have lived with and cooperated with extruder manufacturers and users. (691KB)
      34 Trends in Temperature Control Equipment; Components, Wiring, Operator Interfaces, Configuration, Operation, Support.
    Components, Wiring, Operator Interfaces, Configuration, Operation, Support. Walk round a few process plants and you will see some 20 years of evolution. Starting from the tried and true using discrete Instruments all the way up to SCADA (Supervisory Control and Data Acquisition) systems with colour monitors and operator interfaces, rich in control, protection and data analysis capability.
      35 Checking your Heat Process on a Budget
    Your Test Instruments: Buy two, make two yourself
    You are visiting the job site and suddenly you hear "Oh boy am I glad you're here, we have trouble". You didn't expect this and you have to make do with what test equipment you can find there; even make up what else needed to check the controls on the process. Here's how to make the best of it.
      36 Misfits: Are you being set up for a Human-Error Verdict?
    Too often an inquiry or inquest concludes "Human Error" and somebody is named An instinctive reaction is to search for a person to blame when the finger should rightly be pointing to the unrealistic complex actions expected from that person. All too often the answer lies in neglect of the Human Factor in the design of equipment, documentation and procedures. Here are some reminders from my earlier columns in Process Heating Magazine that point to misfits and complexity between man and technology.


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