Manual Tuning - Watlow 945 Series User Manual

Tuning
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WATLOW Series 945 User's Manual
To start auto-tuning:
1. Press the MODE key until the AUt parameter appears in the data display.
2. Select a thermal response value using the UP/DOWN keys, 1=slow,
2=medium, and 3=fast. A thermal response value of 2 satisfactorily tunes
most thermal systems.
3. Press the MODE key. While the control is in the tuning mode, the lower
display alternately displays the normal information and the prompt At. The
time between alternations is 1 second.
4. When tuning is complete, the displays return to their previous state and AUt
reverts to 0. The 945 installed appropriate PID tuning parameters and saved
them in the non-volatile memory. If a mechanical relay or contactor is
switching power to the load, a longer cycle time may be desirable to
minimize wear on the mechanical components. Typical life of a
mechanical relay is 100,000 cycles.
To abort auto-tuning, the operator must reset the AUt parameter to 0, press
AUTO/MAN twice, or cycle power off and on. In all cases, aborting auto-tune
restores all values to those previous to auto-tuning.

Manual Tuning

For optimum control performance, tune the Series 945 to your thermal system.
The tuning settings here are for a broad spectrum of applications; your system may
have somewhat different requirements. NOTE: This is a slow procedure, taking
from minutes to hours to obtain optimum value.
NOTE:
Tune heating outputs at a set point above ambient temperature.
Tune cooling outputs at a set point below ambient temperature.
1. Apply power to the Series 945 and enter a set point. Begin with these
Operation parameters: Pb = 1, rE/It = 0.00, rA/dE = 0.00, Ct = 5, CAL = 0,
AUt= 0.
2. Proportional Band Adjustment : Gradually increase Pb until the upper
display temperature stabilizes to a constant value. The process temperature
may not be right on set point because the initial reset value is 0.00 repeats per
minute.
3. Reset/Integral Adjustment: Gradually increase rE/It until the upper display
temperature begins to oscillate or "hunt." Then slowly decrease rE/It until the
upper display stabilizes again near set point.
4. Cycle Time Adjustment: Set Ct as required. Faster cycle times sometimes
achieve the best system control. However, if a mechanical contactor or
solenoid is switching power to the load, a longer cycle time may be desirable to
minimize wear on the mechanical components. Experiment until the cycle time
is consistent with the quality of control you want. Ct will not appear on units
with a process output.
Tuning and Operating, Chapter 5