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AUTO TUNE PROCEDURE
1.
Configure the module for the type of Temperature Sensor (V5017). Then program the PID
Control Period (V5020) and Temperature SetPoint (V5001).
a)
The default value for the PID Control Period of two seconds (V5020=20) is sufficient for
most applications. See page 2.20 for a description of PID Control Period.
2.
If heating control action is required then turn off bit 1 in the Mode Word (V5000). This will cause
the output to increase when the temperature is below the SetPoint. Turn on bit 1 for cooling
control. In this case, the output will increase when the temperature is above the SetPoint.
3.
Make the temperature stabilize near the most commonly used SetPoint. Although this step is not
necessary, the time required to tune the loop will be reduced if it is done. There are two ways to
do this.
a)
The easiest way to stabilize the temperature at the SetPoint is to put the Temperature
Controller in ON/OFF control mode (turn off bit 4 in the Mode Word). While in ON/OFF
control mode, the Temperature Controller will estimate the required PID Output Bias
based on the duty cycle of the Output. Note that it may be necessary to increase the
ON/OFF Hysteresis so that the Output does not chatter as the temperature passes
through the SetPoint. When the estimated Output Bias is nearly the same each time the
Output cycles, proceed to step 4.
b)
If the process will not tolerate the Temperature Controller operating in ON/OFF control
mode then select PID Gain and Reset values until the Temperature Controller begins to
move the temperature closer to the SetPoint. Auto Tune Optimization on page 4.4
describes the effect Gain and Reset have on the PID controller. Force the solid state
relay output on and off using bits 14 and 15 of the Mode Word (V5000) and manually
adjust the Output Bias (V5002) to speed up stabilization.
4.
Turn on PID Auto Tune by setting bits 4 and 8 in the Mode Word. Bit 8 should be set using a
one-shot in ladder logic. The Temperature Controller turns off bit 8 when Auto Tune is done.
Auto Tune may be aborted by turning this bit off. During Auto Tune, the process should be in a
steady state condition (prevent load changes during Auto Tune).
5.
After Auto Tune is done, the new calculated PID Temperature Controller settings for Gain
(V5006), Reset (V5007), and Rate (V5010) will automatically be used.
6.
If the settings calculated by Auto Tune are too aggressive (temperature overshoots or oscillates
around the SetPoint too much following a disturbance) then re-tune the loop with bit 10
(minimize oscillation) turned on. If the large disturbance introduced into the process by this Auto
Tune algorithm cannot be tolerated, then Auto Tune Optimization (page 4.4) or manual tuning
(page 4.5) will be required.
CHAPTER 4: LOOP TUNING
4.1
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