Temperature Control Errors - Omron E5ZE Operation Manual

Temperature Control Errors

Process Value Exceeds Set Point
Probable cause
Connections Process value of the E5ZE is abnormal.
Load is connected to the incorrect control point of
the E5ZE and is controlling the heaters with the
control output of the incorrect control point.
Relay driven by control output has contact weld.
SSR is short-circuited.
SSR leakage current is flowing into the heaters.
Settings E5ZE is in reverse operation mode, instead of
direct operation mode, or vice versa.
PID constants of the E5ZE are incorrect.
Control output value of the E5ZE does not
increase because of the restrictions of the set
output limit value.
Control output value of the E5ZE does not
increase because of the restrictions of the set
output change rate limit value.
E5ZE is outputting in manual operation.
Operation
Controlled object is radiating heat.
Controlled object is influenced by large
overshooting.
Overshooting or Undershooting
Probable cause
Connections Process value of the E5ZE is abnormal.
General-purpose temperature sensor with slow
thermal response characteristics is being used to
sense a controlled object with quick thermal
response characteristics.
Settings
E5ZE has a narrow proportional band and small
P constant.
E5ZE has a short integral time or small I
constant.
E5ZE has a short derivative time or small D
constant.
E5ZE is executing ON and OFF control with a P
constant of 0.
Control period is too long when the E5ZE controls
the temperature of an object with quick thermal
response characteristics.
Dead band instead of an overlap band is set with
the E5ZE in heating and cooling control
operation.
54
Remedy
Refer to 4-3 Temperature Sensing Errors for
appropriate troubleshooting.
Correct the wiring of the load.
Replace the relay.
Replace the SSR.
Connect a bleeder resistance to the SSR to
prevent operation with the SSR leakage current.
Correct the operation mode setting.
• Execute auto-tuning.
• Set the PID constants of the E5ZE to the values
suitable to the system.
• Set the output limit value of the E5ZE to an
appropriate value.
• Disable the output change rate limit function of
the E5ZE by setting to 0000.
• Set the output change rate limit value of the
E5ZE to an appropriate value.
Interrupt the manual operation of the E5ZE.
Execute heating and cooling control.
Refer to the following table regarding
overshooting and undershooting for appropriate
troubleshooting.
Remedy
Refer to 4-3 Temperature Sensing Errors for
appropriate troubleshooting.
Change to a sheath-type temperature sensor.
• Increase the P constant keeping within the
range where the response delay caused by the
P constant can be allowed.
• Execute auto-tuning.
• Increase the I constant keeping within the range
where the response delay caused by the I
constant can be allowed.
• Execute auto-tuning.
• Increase the D constant keeping within the
range where the D constant will not have an
undesirable influence on temperature stability.
• Execute auto-tuning.
Execute P or PID control.
Shorten the control period.
Set the overlap band of the E5ZE.
Section 4-4