NOTE: This page contains the general guidelines for PID tuning. Contact a member of the sample environment team for more information about this process or PIDs in general. CCRs use PID zones to apply different heater powers to different set points to prevent overshoot or undershoot.
- Proportional (P): Output heater power = P * error. If you want to control to the third digit after the decimal point, you need to use big numbers like 500. Otherwise a number less than 100 will do.
- Integral (I): Isettings= 1000/ Integration time. The smaller the Isettings, the longer the integration time is and the longer it will take for the system to stablize. For instance, if you want the integration time to be 100 seconds, I=10.
- Derivative (D): The derivative term can be useful in fast changing systems but it is often turned off during steady state control because it reacts too strongly to small disturbances. The D is set proportional to Isettings when used.
- Proportional (P): Output heater power = P * error. It is often used with dil fridge inserts to control at temperatures below 1K. A value of 10 will suffice.
- Integral (I): The integral term is set in seconds and a smaller setting creates a more active integrator. For instance, if you want the integration time to be 100 seconds, I=100.
- Derivative (D): The derivative setting (D) is related to the dominant time constant of the load similar to the integral (I) and is also set in seconds but a smaller setting creates a less active derivative.
- Proportional (P): P term range from zero to 1000. Gain is scaled to reflect the actual heater range and the load resistance. A value of less than 10 will suffice.
- Integral (I): Integrator gain values range from zero to 10,000. The units of this term are Seconds. For instance, if you want the integration time to be 100 seconds, I=100.
- Derivative (D): Derivative gain values have units of inverse Seconds and may have values from zero to 1000. A value of zero turns the Derivative control function off.
Here are some typical PIDs for CCRs
Some additional tips:
- Check out the documentation packet posted on the CCR.
- Activate the RAMP function for smoother setpoint changes.
- Add some manual output (the PID loop will add/subtract power as needed). You typically need about 30% power to maintain 300K.