Tuning and Operating, Chapter 5
WATLOW Series 965 User's Manual
22
Tuning
To start auto-tuning:
1.
Press the MODE key until the AUt prompt appears in the data display.
2.
Select a thermal response value, 1=slow, 2=medium, and 3=fast, using
the Up-arrow/Down-arrow keys. A thermal response value of 2 satisfacto-
rily 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 965 installs appropriate PID tuning parameters and
saves 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 either reset the AUt parameter to 0, press the A/M key
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 965 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 965 and enter a set point. Begin with these
Operation parameters: Pb = 1, rE/It = 0.00, rA/dE = 0.00, Ct = 5.0, CAL = 0,
AUt= 0.
2. Proportional Band Adjustment: Gradually increase Pb until the upper
display temperature stabilizes to a constant value. The process temperature
will not be right on set point because the initial reset value is 0.00 repeats per
minute. (When Pb = 0; rE/It and rA/dE1 are inoperative, and the 965 func-
tions as a simple ON/OFF control.) The HSC parameter determines the
switching differential value.
3. Reset/Integral Adjustment: Gradually increase rE, or decrease It until the
upper display temperature begins to oscillate or "hunt." Then slowly decrease
rE or increase 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
