Tuning
78
Chapter 6
POWERS 535-PROF User's Manual
Potential Problem
Adaptive Tune cannot run if RESPONSE TIME is
inaccurate
Adaptive Tune cannot compensate for PV oscillation
due to hysteresis of output device (e.g., a sticky valve)
Pretune does not develop optimum PID Parameters
Corrective Action
Change the HI LIMIT and LOW LIMIT, or the HIGH
OUT and LOW OUT, and run Pretune again
Change the HI LIMIT and LOW LIMIT, or the
OUT.STEP size and run Pretune again
Change the manual output percentage, or the HI
LIMIT and LOW LIMIT, and run Pretune again
Set a longer TIMEOUT period and/or increase the
OUT.STEP size, and run Pretune again.
Eliminate the noise source (if possible) or increase
the OUT.STEP and run Pretune again
Check the described conditions and make
corrections or repairs
Change the manual output percent and run Pretune
again
Decrease the OUT.STEP size and run Pretune
again
Increase the OUT.STEP size and run Pretune again
Move TUNE PT. (or the Setpoint if TUNE PT. is
Automatic) farther from the process variable and run
Pretune again
Check if any PID values were generated and if they
are acceptable. If not, eliminate noise sources (if
possible) and run Pretune again
Pretune
Type
1
2,3
1,2,3
1
2,3
1,2,3
1,2,3
1,2,3
1,2,3
1,2,3
1,2,3
1,2,3
1,2,3
2,3
2,3
1
1,2,3
Conclusion/Problem
PRETUNE has generated initial PID and the
Dead Time values
PRETUNE had generated initial PID, Response
Time, Band Noise and the Dead Time values
User has aborted PRETUNE before completion
The Process variable went beyond the HI
LIMIT or LOW LIMIT
The Process variable went beyond the HI
LIMIT or LOW LIMIT
The inital process variable was near or beyond
the HI LIMIT or LOW LIMIT
TIMEOUT limit was reached before Pretune
completed
Too much PV noise was detected
PV or Cold Junction break detected during
Pretune
PV HIGH or PV LOW detected during Pretune
SLIDEWIRE break detected during Pretune
Remote SP Break detected during Pretune
The initial control output is outside the high and
low limits defined in the Control menu
The PV moved too quickly to be analyzed
One or more model parameters are calculated
to be zero
The initial PV is too close to the TUNE PT.
The Process variable went beyond the HI
LIMIT or LOW LIMIT
Message
COMPLETED
ABORTED
LIMIT ERR.
TIMEOUT
NOISE ERR.
INPUT ERR.
OUT. ERROR
DATA ERR.
ZERO ERR.
DEV. ERROR
RETRY
If Pretune and Adaptive Tune do not generate optimal PID values for control, check the following menu entries:
When the Pretune function terminates, one of the following messages will appear:
SELF TUNE MESSAGES AND TROUBLESHOOTING
Refer to Chapter 7 for more information on the Self Tune function of the 535 controller.
Message
RESPONSE TIME
NOISE BAND
PRETUNE
Corrective Action
Run TYPE 2 or TYPE 3 Pretune to obtain the correct value,
or enter it manually
Set NOISE BAND large enought to prevent Adaptive Tune
from acting on the oscillation. If oscillation is not acceptable,
consider replacing valve
Wrong pretune TYPE selected. Refer to Chapter 7, the
section on Self Tune
