Function Blocks
Function Block Reference Guide
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2.50 PID Function Block,
continued
2.50.2 Example 2 -
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)
Figure 2-48 Duplex Control Example
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