© 2015 Thorlabs
16
TED200C
3.2.2 Adjusting Temperature Control Loop
Temperature controllers are used to manage the temperature of thermo-electrically heated/
cooled components in experimental setups, independent of external influences. To adapt a
controller to different thermal loads, and to optimize the controller’s response characteristics,
the controlling parameters of the system’s feedback loop must be optimized. All Thorlabs’
temperature controllers provide a PID control loop whose shares (P, I and D share) must be
matched with the thermal load of the device under test. For an optimum adaptation, these
parameters have to be adjusted separately and independent of each other. This section
describes how to optimize the PID parameters in order to get optimum performance from the
TED200C temperature controller.
·
The P share (proportional, gain) can be adjusted with potentiometer "P" (F22).
·
The I share (integral, offset control) can be adjusted with potentiometer "I" (F23).
·
The D share (derivative, rate control) can be adjusted with potentiometer "D" (F24).
Preparation
1. Select "T
ACT
" to display the actual temperature or thermistor resistance (keys F17 or F18).
2. Turn the three potentiometers "P" (F22), "I" (F23) and "D" (F24) completely counter-
clockwise.
3. Switch off the I share to ease the setting of P and D shares: Press key (F25) for at least one
second to switch off the I share. The sensor LED (F19/F20/F21) is flashing to indicate the "I
share off" state.
4. Set the temperature "T
SET
" to a value around room temperature and switch on the TEC
current output (switch "ON" F9).
Adjust P share
Repeatedly increase and decrease the set temperature for about ± (1...2)°C around room
temperature using the tuning knob (F10) or by applying a suitable slow, square-wave signal to
the analog control input "TUNE IN" (R1) at the rear panel. Watch the settling behavior of the
actual temperature "T
ACT
".
Note
The settling behavior can be observed at the "CTL OUT" output (R2).
Increase the P-share gradually by turning potentiometer (F22) clockwise.
Higher values will increase the settling speed. Too high values will increase the amplitude and
number of overshoots or will even make the system instable (continuous oscillation).
The P share is set correctly if the actual temperature remains stable near the set temperature
after only 2 … 3 overshoots.
Adjust D share
Change set temperature again repeatedly for ± (1...2)°C around room temperature while
observing the settling behavior of the actual temperature.
Increase the D share gradually by turning potentiometer (F23) clockwise.
Higher values will decrease the amplitude and number of overshoots. Too high values will
increase again the amplitude and number of overshoots or will even make the system instable.
The D share is set correctly if the actual temperature remains stable at a value near the set
temperature after a minimum of overshoots.
