User`s guide

Appendix B - Loop Application Examples
PID Control Algorithms
240 UMC800 Control Builder User’s Guide Release E
1/01
PID Control Algorithms
Example 1 - Duplex control - PID with heat/cool (duplex) output
Use standard PID Function Block
• Select PID A Duplex or PID B Duplex
• Set to Reverse acting
• Use Tuning Constant Set #1 from 50% to 100% Heat Output
• Use Tuning Constant Set #2 from 50 % to 0% Cool Output
Choose Output Types for Heat and Cool (Current/Current, Current/Time
Proportioning, Time Prop./ Time Prop., etc.), connect each to PID block output.
Use output block scaling to set duplex output spans. Set output scaling Range Lo
and Hi to 50 - 100 % for heat output and 50% to 0% for cooling output,
respectively. You may need to adjust range limits for overlap or deadband as
required.
0%
50%
100%
Output 1 HEAT
Output 2 COOL
100%
100%
0%
0%
Direct acting
control
Reverse acting
control
Heat
Output
Cool
Output
Output
( %)
Or,
Time
Proportioning
Lo - 50%
Hi - 100%
Lo - 50%
Hi - 0 %
(4 mA)
(20 mA)
Example 2 - Cascade control
The Cascade Loop uses 2 PID blocks
with the back calculation pin of the
secondary connected to the primary
loop. This transfers values back to the
primary loop to adjust the PID for
changes due to Manual control.
: