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…5.7.1 Auto-tuning Page
Hysteresis Value
The hysteresis value is entered in engineering units and is used to determine
when to change the controller output value.
'At Set Point' Tuning only – when the process variable crosses the hysteresis
band (plus and minus the hysteresis value), the controller output changes by
plus and minus the
StEP value from its initial starting value. The hysteresis
value should be set as small as possible but larger than the noise in the process
variable signal, to allow the best possible response data.
Set the hysteresis value required (in engineering units).
Auto-tune High Limit
The process variable must be between the high and low limits when auto-tuning
is activated. If the process value exceeds one of these, the auto-tuning cycle is
shut off automatically by reverting to the manual control mode and returning
the controller output to the value set when the auto-tuning was activated. The
high and low values are the limits for cancelling auto-tune execution.
Set the value required (in engineering units), the decimal point is set
automatically.
Auto-tune Low Limit
Set the value required.
Three Term Control Parameters
Select the Proportional, Integral and Derivative terms required.
Control Type
Select:
‘A’ for quickest response with
1
⁄4 wave damping.
or
‘B’ for quickest response with minimum overshoot.
Continued on next page.
PId
HYSt
At–HI
tErMS
P
At–LO
P
Start-up
PI
10.0
100
100
tYPE
A A
b
SP
X
x
4
Type B – Minimum Overshoot
SP
Type A –
1
4
Wave Damping
…5 CONTROL OPERATION
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