Table of Contents
Advertisement
AUTO TUNE SEQUENCE
The auto tune algorithm uses the following sequence of operation to calculate the controller settings.
The state of the auto tune operation is reported by the Auto Tune Sequence Status bits A and B located
in the Alarm Word (V5004).
Bring the temperature to within 1.0 EC (1.8 EF) of the SetPoint. At this step, the ATn LED will
1.
be urned ON and both Auto Tune Sequence Status bits A and B will be off.
Move the temperature 2 EC (3.6 EF) away from the SetPoint (decrease temperature if heating
2.
lop). At this step, the Auto Tune Sequence Status bit A will be on and B will be off.
Wait for the Output Bias to stabilize to within 1.0 EC (1.8 EF) of this temperature. At this step,
3.
the Auto Tune Sequence Status bit A will be off and B will be on.
4.
Bump the output a constant 10%. At this step, both Auto Tune Sequence Status bit A and B will
be on.
5.
If bit 10 of the mode word is on (minimize oscillation) then the controller settings are calculated
after the temperature stabilizes at the new output (this can take a very long time).
If bit 10 of the mode word is off (faster response) then the controller settings are calculated long
before the temperature stabilizes at the new output value.
AUTO TUNE TROUBLESHOOTING
Problem:
Auto Tune stopped and the Auto Tune Fault bit in the Alarm word was turned on (bit 6).
Cause:
During Auto Tune, the controller output reached the full scale positive limit (100%).
Solution:
Choose a SetPoint so that Output is not near full scale limit.
Problem:
Auto Tune "hangs up" during step 4 and never finishes.
Cause:
When Auto Tune bumps the output 10% (V5002=V5002+100), the temperature must
increase at least 1 degree C (1.8 degrees F).
Solution:
If a 10% increase has little or no effect on the temperature then the loop gain is very
large. In this case, PID Control may not offer any performance increase over ON/OFF
Control. If ON/OFF Control is insufficient, then manual PID Tuning will be required.
One method of manual PID tuning is described beginning on page 4.5.
4.2
LOOP TUNING
Advertisement
Table of Contents
