Watlow Series 365 - Manual (Page 10)

10
WATLOW Series 365 User’s Manual
Tuning
Tuning Procedure for PI Controls
365B - XXXX-X0XX
Initial Settings:
•
Proportional band: 5 to 50°F/2.8 to 27.8°C
Maximum proportional band is clockwise (CW), the minimum is
counter clockwise (CCW). See Figure 14.
Figure 15 -
PI Adjustment
Graph
Figure 14 -
Proportional Band
Potentiometer
Location
• Cycle time, fixed. Typically 6 seconds.
• Automatic reset, fixed. Typically 0.25 repeats/minute.
Energize the system and allow the process temperature to stabilize. When the
system is stable, the load will cycle at a constant rate.
Once an adjustment is made, the system may become unstable. Allow sufficient
time for the system to stabilize before making another adjustment.
Proportional Band Adjustment:
Rotate the proportional band pot CCW 1/4 turn and observe system stability.
Repeat until the process temperature begins to hunt (becomes unstable). When
hunting is observed, rotate the pot CW, in small increments, until the system
becomes stable. Some systems may be stable enough to allow minimum propor-
tional band (maximum CCW).
Top View
Proportional Band
Potentiometer
k
NOTE:
The tuning proce-
dure must be per-
formed with the
control chassis in
the case. Make any
potentiometer
adjustments
through the slots in
the case.
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