Omron EJ1 User Manual page 204

Determining the Error from the Current Situation for Temperature Control Errors
Overshooting or Undershooting
Connection Measured temperature is wrong.
A general-purpose thermometer with slow thermal response
has been connected to a control system with fast thermal
response.
Setting The proportional band value is too low.
The integral time is too short.
The derivative time is too short.
ON/OFF control is operating.
The control cycle is too long for the control system with its
fast thermal response.
The overlap band in the heating and cooling control is set to
a dead band by mistake.
Hunting
The troubleshooting items for connection and setting problems are the same as for overshooting and under-
shooting, above.
Procedure The heater's heating capacity is too large for the heating
capacity of the control target.
There is periodic disturbance, which changes the heating
capacity of the control target.
Executing autotuning (AT).
Possible cause
Possible cause
Countermeasure
• Perform the action outlined in 7.5.
• Change to a sheathed thermometer.
• Increase the proportional band within a range with an
acceptable response delay.
• Execute autotuning (AT).
• Increase the integral time within a range with an acceptable
response delay.
• Execute autotuning (AT).
• Increase the derivative time within a range that does not
adversely affect the stability of stabilization time.
• Execute autotuning (AT).
• Execute P control or PID control.
• Shorten the control cycle.
• Set to an overlap band.
Countermeasure
• Use a heater with a heating capacity suitable for the control
target.
• Change to an environment with as little periodic distur-
bance.
• Hunting will not occur once autotuning has been completed.
Section 7-6
183