TE Technology TC-36-25-RS485 - Manual (Page 27)

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If the bandwidth is set too narrow, the temperature will oscillate around the set point. If the bandwidth is too
wide, the controller will be slow to respond or may never reach set point.
INTEGRAL GAIN:
The acceptable values that may be entered are (0.00 to 10) repeats per minute.
With just proportional control, the controller’s output is, by definition, 0% when the actual temperature reaches
the set temperature. Because some non‐zero output power level is almost always required to reach the set point,
using only proportional control will not allow the controller to maintain a desired set point. Therefore, introducing
an integral gain allows for an output amount other than 0% when the actual temperature reaches the set
temperature. It essentially shifts the output power to the average level required to maintain the desired set point.
For example, suppose the set temperature is 10.0 °C, the bandwidth is set to 5 °C, and the controller settled to a
constant 11.2 °C (corresponding to 48% power with only the proportional bandwidth active).

In this case the “error”, or difference in temperature between the set point and actual temperature, is 1.2 °C.

From the example in section 3.3 we know that the proportional output will change by 40% for every 1 °C
change in the error (this is bandwidth gain of 40 % per °C).

Let’s assume the integral gain is activated by changing its setting from “0” to “1 per minute”.
The integral function will now ramp the output at a rate determined by the error signal, the proportional
bandwidth gain, and the integral gain. The rate is determined by multiplying the error, the bandwidth gain, and
the integral gain. In this case, if the integral control is set to 1 repeat per minute, the controller will increase the
output power at a rate of 48% per 1 minute.
This output % is updated continuously. Of course, the maximum output is limited to +100% and the minimum is
limited to ‐100%.
If the integral gain is set too high, the temperature will oscillate. If integral control is set too low, it will take a long
time for the temperature to settle to steady state.
DERIVATIVE GAIN:
The acceptable values that may be entered are (0.00 to 10) cycles per minute.
The derivative gain senses the rate of change of the temperature and allows the controller to anticipate the power
needed to compensate for rapid changes in system loading. This term is generally used only on very sluggish
systems or where very quick response is necessary. It works in a way similar to the integral gain, but acts upon
change in error signal and not the actual error signal.
The method of determining the proper parameters for proportional bandwidth, integral gain, and derivative gain is
described in Section 3.0.
DEADBAND
The controller can be set to turn on and off by either rising or falling temperatures where no heating or cooling
takes place. This band is expressed in degrees, and the acceptable values that may be entered are 0.1 to 100. This
setting is only utilized when CONTROL TYPE is set to DEADBAND CONTROL.
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min
48%
min
1
C 1.2
C
% 40  
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