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Back-up Control with KS 94
备份控制策略
The KS 94 does not have an input for YHM (hard manual). Nevertheless a little
trick allows the realisation of a back-up control loop. In this special case
the controller outputs must control a motorized valve, accordingly we need
3-point stepping outputs.
1 DESCRIPTION
The output of the master controller, e.g. realized as a PLC function,
is connected as a 4...20mA signal to the OVC+ input of the KS 94 controller. As
long as this signal is ok, the motor position will follow. If the master
fails, the currant is “0” and the KS 94 takes over the control loop
in complete automatic mode. Via digital input di10 the OVC function can be
switched off.
1.1 Option (gray lines)
If the KS 94 should use the last process value as setpoint, the KS 94
must be switched to external setpoint during back-up mode and the x-tracking
function must be activated.
2 INSTRUMENT VERSION
KS 94/TPS with option C (The TPS voltage is used to supply the di1/di2
input)
3 ADJUSTMENT
3.1 Configuration
3.1.1 Possible Controller Types
2-Point, 3-Point, continuous, continuous controller with positioner
3.1.2 Additional Configuration
Setpoint/cascade control; process value tracking (option)
OVC+ (INP4) as 4..20mA ð sensor fail: xFail=100% and OUT4 switches over
y/Y2 via di1.
 
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2003 PMA Prozeß- und Maschinen- Automation GmbH
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