Watlow 8LS Controller - Manual (Page 90)

82 8LS User’s Guide
Tuning and Control
General PID Constants by Application
This section gives PID values for many applications. They are useful as
control values or as starting points for PID tuning.
Proportional Band Only (P)
PB: Set the PB to 7% of the setpoint (SP) (Example: Setpoint = 450, so
Proportional Band = 31).
Proportional with Integral (PI)
PB: Set the PB to 10% of SP (Example: Setpoint = 450, so PB = 45).
Set TI to 60.
Set TD to Off.
Set the Output Filter to 2.
PI with Derivative (PID)
PB: Set the PB to 10% of the SP (Example: Setpoint = 450, so PB = 45).
Set the TI to 60.
Set the TD to 15% of the TI (Example: TI = 60, so TD = 9).
Set the Output Filter to 2.
The next table shows general PID constants by application.
Application PB TI TD Filter Output Type Cycle Time Action
Electrical heat w/ SSR
(Solid State Relays) 50 º 60 15 4 TP or
DZC
3 Reverse
Electrical heat w/
Mechanical relays 50 º 60 15 6 TP 20 Reverse
Gas heat with motor-
ized valves 60 º 120 25 8 ANA NA
Gas heat SP>1200 100 º 240 40 8 ANA NA
Extruders w/cooling
Heat w/SSR
Set spread to 0 50 º 300 90 8 Cool-TP
Heat-DSC
3 Reverse
Cool w/ solenoid valve 10 º Off Off 4 TP 20 Direct
Cool w/ fans 10 º off Off 4 TP 60 Direct
Electric heat w/ open
heat coils 30 º 20 off 4 DZC NA Reverse
Electric heat w/ SCR
Controllers 60 º 60 15 4 ANA NA Reverse