Micromod Micro-DCI: 53SL5100A Single Loop Controller - Manual (Page 108)

Single Loop Process Controller Instruction Manual
100 Instrument Tuning
10.3 Derivative Action (TD)
Derivative action augments proportional action by responding to the rate of change of the process variable.
It is used to make the controller more responsive to sudden process disturbances.
The datapoint to set the Rate parameter is C108; it has a default value of 0 minutes.
The minimum value for derivative action is 0.01 minutes and the maximum time is 8 minutes; 0 is off.
The derivative time in minutes is the amount of time by which the proportional action (or proportional plus
integral action) is advanced.
10.4 Instrument Tuning
Table 10-1 provides summary information for the tuning parameters referenced in the three tuning meth-
ods that follow. The Trial and Error Method ( Table 10-2 ) is usually preferred for processes that respond
quickly, requiring no waiting to determine steady cycling process conditions. The Proportional Cycle
Method (
Table 10-3 ) and Step Response Method ( Table 10-4 ) are expedient procedures for slow pro-
cesses. See Figure 10-1 for a graphical representation of the Step Response Method.
Table 10-1. Summary Information for Tuning Parameters
Abbr. Datapoint Minimum Value Maximum Value Parameter
P.B. C106 2% 1000% Proportional Band
TR C107 0.02 minutes/rep. 200 minutes/rep. Reset
TD C108 0.01 minutes 8 minutes Rate
Table 10-2. Trial and Error Tuning Method
Step Procedure
1 Set the process to approximately normal conditions in Manual mode.
2 Set TR (C107) first to minimum value (0.02 minutes) for several moments, then set it
to the extreme maximum (200 minutes) to lock in a fixed reset value.
3 Set P.B. (C106) to the widest value (1000%).
4 Set TD (C108) to the lowest value (0.01 minutes).
5 Switch to Auto mode.
6 Slowly reduce P.B. (C106) until process cycling starts.
7 Increase TD (C108) slowly until process cycling stops.
8 Reduce P.B. (C106) until process cycling starts again.
9 Further increase TD (C108) until cycling stops again.
10 Repeat Steps 8 and 9 until no improvement can be made when TD is increased.
11 Increase P.B. (C106) to a safe margin approximately 1.5 times the value attained in
Steps 8 through 10.