An introduction to temperature control

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An introduction to temperature control

  1. 1. WEST Control Solutions – Your global partner for measurement and control technology An Introduction to Temperature Control
  2. 2. WEST Control Solutions – Your global partner for measurement and control technology Basic temperature control (+/- 2˚ or 3˚) Thermostat Output switching 18, 19, 20, 21, 22 Room temperature measurement Switching: on when under temp’ And off when over temp’ 2
  3. 3. WEST Control Solutions – Your global partner for measurement and control technologyClosed-loop control: Component parts Controller Control Device Loop Heater 3
  4. 4. WEST Control Solutions – Your global partner for measurement and control technologyInputsControllers have many types of inputs Thermocouple DC Linear • B, C, J, K, L, N, R, S, T • Volts • millivolts Remote Setpoint • Milliamps • Volts • millivolts RTD (Resistance Temperature Device) • milliamps • PT100 • Potentiometer • NI120 4
  5. 5. WEST Control Solutions – Your global partner for measurement and control technologyThermocouples• A thermocouple is made from two wires of different metal types, welded at one end (the “Hot” Junction).• The wires are connected to the controller (the reference or “Cold” junction).• When a difference in temperature exists between the “Hot” and “Cold” junctions, a small electric current will flow, in proportion to the temperature difference (this is called the thermoelectric effect). 5
  6. 6. WEST Control Solutions – Your global partner for measurement and control technologyThermocouple Colour Codes • For the different types of metals various letters and colours are used. • These colours vary from country to country but most now use the international IEC584 standard 6
  7. 7. WEST Control Solutions – Your global partner for measurement and control technologyRTD (Resistance Temperature Device)• An RTD is made of a material that changes its resistance in a predictable way with changes in temperature• There are many types of RTD the most common of which is the PT100 (Platinum Resistance Thermometer )• The PT100 has a resistance of 100Ω at 0°C 7
  8. 8. WEST Control Solutions – Your global partner for measurement and control technologyOutputs OverviewThere are 5 main output types • Relay • SSR Driver • Triac • Transmitter Power Supply • DC Linear > Volts > Millivolts > milliamps 8
  9. 9. WEST Control Solutions – Your global partner for measurement and control technologyClosed-loop control: Terminology• LOAD - unit to be heated• HEATER - electrical or gas• INPUT - thermocouple, PT100, DC• CONTROLLER - decision making unit• OUTPUTS - solid-state relay (SSR) - electro-mechanical relay - DC Volts or milliamps 9
  10. 10. WEST Control Solutions – Your global partner for measurement and control technology On/Off Control Temp Output turns off – just like home thermostatSet-point Hysteresis Output turns on Time 10
  11. 11. WEST Control Solutions – Your global partner for measurement and control technology Proportional Only Control Temp Offset - requires manual adjustment to remove 0% power PropSet-point band 100% power Time 11
  12. 12. WEST Control Solutions – Your global partner for measurement and control technology Conventional P.I.D. Control Temp 0% power PropSet-point band 100% power Time 12
  13. 13. WEST Control Solutions – Your global partner for measurement and control technology Cycle-time (time proportioning)On/Off e.g. 50% power on off on off on off on Time Cycle time e.g. 10 secs e.g. 75% power on off on off on off on off 13
  14. 14. WEST Control Solutions – Your global partner for measurement and control technologyCycle-time & Proportional band Temp PropSet-point band 100% power 0% power e.g. 65% power Time on on on on off off off Cyc’ time e.g. 10s 14
  15. 15. WEST Control Solutions – Your global partner for measurement and control technology Integral Time (minutes) Too short Too long • Corrects proportional control offset error • Too short - overshoots and oscillates • Too long - slow warm-up and response 15
  16. 16. WEST Control Solutions – Your global partner for measurement and control technologyDerivative Time (seconds) Too short Too long • Suppresses overshoots • Effects response time to disturbances • Too short - slow warm-up/response • Too short - under corrects • Too long - oscillates and over corrects 16
  17. 17. WEST Control Solutions – Your global partner for measurement and control technologyContinuous (analogue) Control & Prop-Band Temp PropSetpoint band 100% power 0% power e.g. 65% power Time 20mA 4mA 17
  18. 18. WEST Control Solutions – Your global partner for measurement and control technologyTuningAutomatic Tuning • Selects optimal PID values automaticallyStart-Up Tuning • Tests process when heating upTune at setpoint • If process near ambient or can’t be interruptedContinuous Tuning • Monitors and adjusts if process moves from set-point 18
  19. 19. WEST Control Solutions – Your global partner for measurement and control technology Typical Start-up Auto-tuning Temp Auto-tune completes & enters PID valuesSetpoint Start tune (self-learning) at 50% or 75% of setpoint Time 19
  20. 20. WEST Control Solutions – Your global partner for measurement and control technology Typical Tuning at Set-point Temp Overshoots during tuningSetpoint Auto-tune completes & enters PID values Start tune (self-learning the process) @ 100% of setpoint Time 20
  21. 21. WEST Control Solutions – Your global partner for measurement and control technology Self-tune • Self-tune is a continuous improvement of the PID terms • Self-tune monitors for oscillations in the PV • After 5 oscillations new PID terms are calculatedTemperatureSetpoint 2 Load DisturbanceSetpoint 1 Setpoint Change Time 21
  22. 22. WEST Control Solutions – Your global partner for measurement and control technologyProcess Alarm Types• Deviation high or low alarm• Deviation band alarm• Full-scale high or low alarm Deviation high or low Band Full scale high or low 22
  23. 23. WEST Control Solutions – Your global partner for measurement and control technology Typical Applications Industry Applications Plastics Extrusion, Blown-film extrusion, Hot-runners Window-frames Packaging Bag sealers, Blister packaging, Wrapping Food & beverage Ovens, Chillers, Packaging, Bottling, drying, Heat tunnels Life sciences Incubators, Analytical equipment, Lab equipment, Sterilizers Metals Foundries & furnaces, Metal treatment Electrical, electronic Reflow ovens, Solder baths Composite materials Autoclaves, Curing ovens Glass & Ceramics Kilns & furnaces 23
  24. 24. WEST Control Solutions – Your global partner for measurement and control technology Thank you. For more information please contact the Technical Support Team. Juni 12 24

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