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CAUTION: Before selecting valve “Open”mode check Instrument Inlet
Pressure! Make sure the differential pressure transient during valve
opening will not exceed sensor maximum differential pressure. Improper
usage may lead to damage of the instrument pressure sensors! Do not
activate valve “Open”mode if instrument has more than 10 PSIG applied
to the inlet and instrument output is connecting to the atmosphere!
NOTE: The Valve Mode menu selection only available from main PI screens 1 to
4 (see fi gure 10)
The "Local & Digital Set Point Merge" parameter if enabled allow change set point value
via digital interface even the Set Point Source is assigned to "Local Interface". The "Local
Set Point Auto Start" parameter if enabled will automatically set valve mode in "Auto" after
power is applied and start last saved Local Set Point execution (if Set Point Source param-
eter is set to "Local"). Consult factory for more information.
CAUTION: DPC instrument Valve PID parameters were adjusted on the
factory according to your order and they allow to handle most applications.
Do not change PID parameters unless instructed by factory technical support
representative! It is recommended to contact factory technical support if DPC
instrument exhibit any problem with stability, response time or different PID
parameters are required for your application.
6.4.4 Controller PID Parameters
PID Parameters determine the performance of proportional valve control algorithm. P refers
to the Proportional term of the PID loop, I refers to the Integral term of the PID loop and
D refers to the Differential term of the PID loop. These values impact control speed, valve
stability, overshoot, undershoot and oscillation. DPC instruments shipped from the factory
with a generic PID values designed to handle most applications. If your application required
different settings (there are issues with valve stability, oscillation or speed), adjustment of
these parameters may resolve the problem.
DPC instruments support 3 different implementations of the PID control loop algorithm: PD,
PID and PIDD.
The PD algorithm is the default algorithm used on most DPC controllers and usually works
fi ne for most generic applications with wide range of the differential pressure across the
valve. With this algorithm the Integral term is disabled (not used).
NOTE: If PID loop type is changed, the PID parameters may need to be adjusted
to work properly with different PID loop type.
The PID Loop Type can be selected from “Valve PID Loop Type” menu selection in the
“Valve Parameters” menu.
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