TM 5-3895-374-24-2
955-257
5.
Bring the process to setpoint with the controller in the loop and observe response. If the response has too much
overshoot, or is oscillating, then the PID parameters can be changed (slightly, one at a time, and observing process
response) in the following directions:
Widen the Proportional Band, lower the Reset value, and increase the Rate value.
Example:
The chart recording to the right was obtained by applying
full power to an oven. The chart scales are 10F/cm,
and 5 min/cm. The controller range is 100-600F, for a
span of 500F.
Max. slope = 18F/5 min
= 3.6F/min
Time delay = Td = approximately 7 min
PR Band = 7 min X 3.6 F/min
X 100/500F = 5%
Reset = 0.4/7 min = 0.06 Resets/min
Rate = 0.4 X 7 sin = 2.8 min
ECLIPSE INSTRUMENTATION DIVISION
page 3-1103
