Appendix - Conair Thermolator TW-S User Manual

PID Para me te r s
The Conair TW-S and TW-P Thermolator features a PID ("proportional-integral-
derivative") control-loop algorithm implemented in the programming of the control-
ler board. This algorithm is used to achieve the proper temperature of the process fluid
quickly and accurately. The following tables and paragraphs describe its operation.
The default factory PID parameters loaded into the TW-S and TW-P should work well
under most applications. However, due to a wide variety of situations and system
requirements, these parameters can be adjusted to best serve a particular application.
Default
Proportional band
20
Derivative time
Integral time
25
Proportional band ratio
Proportional
The main driver for the Thermolator control loop is the proportional response. Propor-
tional logic is very simple—it selects a heating or cooling level (strength) based on how
close the process temperature is to the setpoint.
The proportional parameter defines a band over what range of degrees the temperature
controller will taper-off its heating or cooling. Heating/Cooling will be applied at 100%
if the process temperature is more than the band parameter away from the setpoint. A
smaller number will produce a more aggressive proportional response because it will
shrink the band.
If the Thermolator is not providing a strong enough heating or cooling response for a
given situation, this parameter number should be made more aggressive (a smaller number
should be used).
Typical values would be 1% to 30% of setpoint. The cool proportional band and the heat
proportional band are factory set to the same number. If you have a very warm external
cooling water source, you may want to make the cool proportional band number smaller
than the heat proportional band. Likewise, if your cooling water source is very cold, you
may want to make the cool proportional band larger than the heat proportional band.
PID Default Parameters
Controller
Parameter
bn
Smaller number = more aggressive proportional cooling response.
Er
5 Larger number = more aggressive derivative cooling response.
nt
Smaller number = more aggressive integral cooling response.
Pbr
5 Used to adjust closing vs. opening strength of floating valve.
Comments
(Continued)
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