Overshooting Or Undershooting Occurs; Hunting Occurs - Omron E5AR-T User Manual

Direct operation and reverse operation settings are
incorrect.
The PID constants are not suitable.
The output does not decrease due to MV limits.
Output is taking place in Manual Mode.
The controlled object generates heat.
Large overshoot.

■ Overshooting or Undershooting Occurs

Abnormal measured value.
A regular slow thermal response temperature
sensor is connected to a fast thermal response
control system.
The proportional band is too narrow, i.e., the P
constant is too small.
The integral time is too short, i.e., the I constant is
too small.
The derivative time is too short, i.e., the D constant
is too small.
ON/OFF control is being performed.
The control period is too long in a fast thermal
response control system.
The overlap band is mistakenly set as a dead band
in heating/cooling control.

■ Hunting Occurs

Check connections and settings as explained above in Overshooting or Undershooting Occurs.
The heat capacity of the heater is too large for the
heat capacity of the controlled object.
Periodic disturbances occur that cause the heat
capacity of the controlled object to change.
AT is being executed.
10.4 Inferring Causes from Conditions: Abnormal Control
Possible cause
Possible cause
Possible cause
Solution
Set the correct settings.
• Execute AT.
• Set suitable PID constants.
Change the MV limits to suitable values.
Leave Manual Mode.
Use heating/cooling control.
See the Overshooting or Undershooting Occurs
troubleshooting table.
Solution
Troubleshoot as described in 10.3 Inferring
Causes from Conditions: Abnormal Measured
Values (P. 10-4).
Change to a sheathed temperature sensor.
• Increase the P constant to within the point where
the response speed becomes too slow.
• Execute AT.
• Increase the I constant to within the point where
the response speed becomes too slow.
• Execute AT.
• Increase the D constant to within the point where
stability during rectification deteriorates.
• Execute AT.
Use P control or PID control.
Shorten the control period.
Set an overlap band.
Solution
Use a heater with a heat capacity suitable for the
controlled object.
Establish an environment will minimal
disturbances.
Hunting will stop when AT has been completed.
10-7