User manual

PID Loop Operation
(DL450 Only)
Maintenance
8--43
PID Loop Operation (DL450 only)
DL405 User Manual, 4th Edition, Rev. A
The foregone method is the most common method used to tune a PID loop.
Derivative gain is almost never used in a temperature control loop. This method can
also be used for other control loops, but other parameters may need to be added for
a stable control output.
Test your loop for a high PV of 80% and again for a l ow PV of 20%, and correct the
values if necessary. Small adjustments of the parameters can make the control
output more precise or more unstable. It is sometimes acceptable to have a small
overshoot to make the control output react quicker.
The derivative gain can be helpful for those control loops which are not controlling
temperature. For these loops, try adding avalue of 0.5 for the derivative gain andsee
if this improves the control output. If there is little or no response, increase the
derivative by increments of 0.5 until there is an improvement to the output trend.
Recall that the derivative gain reacts with a rate of change of the error.