Download Twido programmable controllers

Advanced Instructions
Troubleshooting
Errors of the
Auto-tuning
Function
The following table records the auto-tuning error messages and describes possible
causes as well as troubleshooting actions:
Error Message
Possible Cause
Autotuning error: the
process variable (PV) limit
has been reached
The process variable is reaching This is a system safety.
the maximum value allowed.
As the AT is an open-loop process, the Process
Variable (PV) Limit works as an upper limit.
Explanation / Possible Solution
Autotuning error : due to
either oversampling or
output setpoint too low
Any of two possible causes:
Increase either the sampling period or the AT
z Sampling period is too small. Output Setpoint value.
z AT Output is set too low.
Autotuning error: the time
constant is negative
The sampling period may be too For more details, please check out PID Tuning With
large.
Auto-Tuning (AT), p. 549.
Autotuning error: error
calculating Kp
The AT algorithm has failed (no
convergence).
Check the PID and AT parameters and make
adjustments that can improve convergence.
Check also that there is no disturbance that could
affect the process variable.
Autotuning error: time
constant over delay ratio >
20
τ/θ > 20
PID regulation is no longer guaranteed.
For more details, please check out PID Tuning With
Auto-Tuning (AT), p. 549.
Autotuning error: time
τ/θ < 2
constant over delay ratio < 2
PID regulation is no longer guaranteed.
For more details, please check out PID Tuning With
Auto-Tuning (AT), p. 549.
Autotuning error: the limit for Computed value of static gain
Kp has been exceeded
(Kp) is greater than 10000.
Measurement sensitivity of some application
variables may be too low. The application's
measurement range must be rescaled within the [010000] interval.
Autotuning error: the limit for Computed value of integral time Computational limit is reached.
Ti has been exceeded
constant (Ti) is greater than
20000.
Autotuning error: the limit for Computed value of derivative
Td has been exceeded
time constant (Td) is greater
than 10000.
556
Computational limit is reached.
TWD USE 10AE