Micromod MOD: Modcell 2050R Users Guide - Manual (Page 167)

IB-23C650
TUNING
Table 13. Autotune Procedure
Middle
Display
Bottom
Display
Entry Description
xxx
Process
Value
ATN is displayed to indicate the Autotune
point of entry.
STEP SIZ 10.1 Valid values are 0.1 to 50.0.
The controller output will change by plus and
minus the output step size from its initial
starting value when autotune is executed (refer
to Figure 18). This value should be large
enough so that the amplitude of the process
variable excursions is at least 4 times larger
than the hysteresis parameter. This will allow
the best possible response data. The output
step size should also be small enough to avoid
crossing either of the process variable trip-
points.
HYST 2.0 Valid values are: 0.1 to 3000.0, or 0.01 to
300.00, or 0.001 to 30.000.
The hysteresis value is used in determining
when to change the controller output value
(refer to Figure 18). When the process variable
crosses the hysteresis band (plus and minus
the [
HYST ] value), the controller output will
change by plus and minus the [STEP SIZ]
value from its initial starting value. The
hysteresis value must be set so that it is larger
than the noise in the process variable signal,
allowing best possible response data.
CAUTION
The value of the hysteresis parameter must
be greater than the process noise value,
including any contribution of time
proportioning cycling to process signal
noise. If hysteresis does not exceed noise,
the autotune calculations may be
inaccurate.
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