Error Messages; Appendix A: Autotuning - Fuji Electric PXV3 SERIES Operation Manual

ERROR MESSAGES

Error
Indication Cause
1. Thermocouple burnt out.
2. RTD (A) leg burnt out.
3. PV value exceeds P-SU
by 5% FS.
1. When RTD (B or C) is
burnt out.
2. When RTD (between
A and B, or between
A and C) is shorted.
3. When PV value is below
P-SL by 5% FS.
4. When analog input wiring
is open or short.
When PV value goes below
-1999.
HB lamp ON Heater break condition
When the setting of
P-SL/P-SU is improper
Fault in the unit
Control Output
When the burn-out
control output is set for
lower limit (standard):
OFF, or 4mA or less.
When the burn-out
control output is set for
upper limit: ON, or 20mA
or less.
Control is continued until
the value reaches -5% FS
or less, after which burn-
out condition will occur.
Normal control output for
heating is continued.
OFF, or, 4mA or less.
Undefined. Stop use
immediately.
18
APPENDIX A
Autotuning
By autotuning, the controller selects what it calculates to be the opti-
mal PID control parameters for a particular process and then stores
them in EEPROM memory for future use. The PID parameters are
stored so that when the controller is powered up after being shut
down, the controller does not need to be autotuned again. The con-
troller uses the same autotuned PID parameters until the Autotune
function is again initiated. The Autotune parameters are only good for
the process the Autotune function was used on. If the setpoint is sig-
nificantly changed, the input sensor is changed, the load or output
device is changed or relocated, or any other disturbances occur
which might change the dynamics of the system, the Autotune func-
tion should be performed again. The autotuned control parameters
are not always perfect for every application but almost always give
the operator a good starting point from which further refinement of
the control parameters can be performed manually.
The autotuning algorithm used here is particularly suited for tempera-
ture control applications and may not always autotune effectively for
other processes. Here are cases where the Autotune function does
not perform well or does not perform at all:
1. The system is affected by process disturbances external to the con-
trol loop. Adjacent heater zones, changing material levels, exother-
mic reactions are examples of process disturbances which are
external to the control loop. The controller would never be able to
autotune such an unstable process.
2. The system is very dynamic. The process variable changes very
quickly. Certain pressure and flow applications would be charac-
terized as very dynamic. Because of how the Autotune function is
performed, a very dynamic system would create very large over-
shoots which could damage the process.
3. The system is very insulated and cannot cool down in a timely man-
ner. With such heating systems the autotuning function would take
a long time to complete, with questionable results.
During autotuning test signals are sent to the process. The test sig-
nals are 100% output and 0% output at the Autotune point. The
Autotune point can either be at setpoint or 10% of full scale below
setpoint.
The controller performs as an On/Off controller. See diagram below.
Autotune
Point
Process
Variable
ON
100%
Output
0%
Autotune Period
Time
OFF ON OFF ON
Time