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A) Enter the setpoint at its working value.
B) Set the proportional band at 0.1% (with on-off type setting).
Process
Variable
Peak
How to switch the unit OFF: hold down the "F" and "Raise" keys simultaneously for 5 seconds to deactivate the unit, which
will go to the OFF state while keeping the line supply connected and keeping the process value displayed. The SV display is
OFF.
All outputs (alarms and controls) are OFF (logic level 0, relays de-energized) and all unit functions are disabled except the
switch-on function and digital communication.
How to switch the unit ON: hold down the "F" key for 5 seconds and the unit will switch OFF to ON. If there is a power failure
during the OFF state, the unit will remain in OFF state at the next power-up (ON/OFF state is memorized).
The function is normally enabled, but can be disabled by setting the parameter Prot = Prot +16.
Enabling the auto-tuning function blocks the PID parameter
settings.
Is activated via the Stu parameter (values 1, 3).
It continuously reads system oscillations, immediately seeking
the PID parameter values that reduce the current oscillation.
It does not engage if the oscillations drop below 1.0% of the
proportional band. It is interrupted if the set-point is changed,
and automatically resumes with a constant set-point.
14
8 • MANUAL TUNING
C) Switch to automatic and observe the behavior of the variable. It will be
similar to that in the figure:
D) The PID parameters are calculated s follows: Proportional band
T
P.B.= ---------------------------------------- x 100
(V max - V min) is the scale range.
Integral time: It = 1.5 x T
Derivative time: dt = It/4
E) Switch the unit to manual, set the calculated parameters. Return to PID
action by setting the appropriate relay output cycle time, and switch back to
Time
Automatic.
F) If possible, to optimize parameters, change the setpoint and check
temporary response. If an oscillation persists, increase the proportional
band. If the response is too slow, reduce it.
9 • SOFTWARE ON / OFF SWITCHING FUNCTION
10 • AUTO-TUNING
Peak
(V max - V min)
The calculated parameters are not saved if the instrument is
switched off, if the instrument is switched to manual, or if the
configuration code is disabled.
The controller resumes with the parameters programmed
before auto-tuning was enabled.
81503D_MHW_400-401_12-2010_ENG
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