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