Watlow Series 935B - Manual (Page 35)

Watlow Series 935B User’s Manual 35
Tweaking PID Settings
1. Set [Pb`h] and [Ct`h] in degrees.
2. If Proportional Band Heat [Pb`h] = 0, Set Hysteresis Heat [HySh] . The Series 935B will
provide on/off control with the hysteresis value selected, and no proportioning action.
3. Proportional Bands should be decreased for tighter control but increased to eliminate
oscillations.
4. Cycle Time Heat [Ct`h] is limited to a minimum of 5.0 seconds for the electromechanical
relay to help reduce wear. The electromechanical relay (D, Output 2) is not recommended
for PID control. It is warranted to 100,000 contact closures only. Alarm or on/off control are
appropriate applications for the Series 935B's electromechanical relay output.
5. Set Dead Band [``db] to adjust the effective cool set point above the primary set point by
the dead band value in degrees. In cool/heat applications, dead band prevents continuous
cool output action by creating a buffer between heating and cooling output action.
6. Set [Pb`c] and [Ct`c] in degrees.
7. If Proportional Band Cool [Pb`c] = 0, Set Hysteresis Heat [HYSc] . The Series 935B will
provide on/off control with the hysteresis value selected, and no proportioning action.
8. Proportional Bands should be decreased for tighter control but increased to eliminate
oscillations.
9. Cycle Time Heat [Ct`h] is limited to a minimum of 5.0 seconds for the electromechanical
relay to help reduce wear. The electromechanical relay (D, Output 2) is not recommended
for PID control. It is warranted to 100,000 contact closures only. Alarm or on/off control are
appropriate applications for the Series 935B's electromechanical relay output.
10. Set Integral [``It] to eliminate droop in the system. Lower the value for more droop
reduction. Adjustable from 0 to 99.9 minutes / repeat.
11. Set Derivative [``dE] to prevent overshoot. Increasing the value slows the approach to
set point. Adjustable from 0 to 9.99 minutes.
12. Calibration Offset [`Cal] eliminates the difference between the displayed process
temperature and the actual process temperature value.
PID Menu
Set up Heat:
[Pb`h]
✓
Proportional Band
[hySh]
✓
Hysteresis
[Ct`h]
✓
Cycle Time
[``db]
✓
Dead Band
Set up Cool:
[Pb`c]
✓
Proportional Band
[hySc]
✓
Hysteresis
[Ct`c]
✓
Cycle Time
Set up General:
[``It]
✓
Integral
[``dE]
✓
Derivative
[`CAL]
✓
Calibration Offset