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5 Optimization of Temperature Control

5.2 PID Adjustment

Temperature control loops are comparatively slow; control oscillations appear with a frequency in

the range of several Hz or parts of Hz. The PID adjustment allows to optimize the dynamic behavior.

The ITC8000 modules allow to set the three parameters P, I and D independently within the range

from 0.1% to 100%.

Example of a PID adjustment

(Pre-conditions: All limit values have been set correctly, all polarities are correct, all set and

relevant calibration values are entered, ambient temperature is about 20°C)

· Switch off the I-share.

· Set the P-, I- and D-share to 1%. Please refer to section Setting the P, I and D Share of the

Control Loop .

· Switch on the output and observe the temperature.

P-share

· Change the set temperature repeatedly between 18 °C and 22 °C while observing the settling

behavior of the actual temperature.

· Increase the P-share gradually. Higher values will increase the settling speed, too high values

make the system oscillate.

The P-share has been set correctly when the actual temperature remains stable near the set

temperature after 2-3 overshoots.

D-share

· Change the set temperature repeatedly between 18 °C and 22 °C while observing again the

settling behavior of the actual temperature.

· Increase the D-share gradually. Higher values will decrease the amplitude of the overshoots.

The D-share is set correctly when the actual temperature remains stable near the set temperature

after a minimum of overshoots.

I-share

· Turn on the I-share.

· Change the set temperature repeatedly between 18 °C and 22 °C .

· Increase the I-share gradually. Higher values will accelerate the settling to the set

temperature.

The I-share is set correctly when the actual temperature reaches the set temperature in shortest

time without overshoots.

THORLABS ITC8000 User Manual

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