<7. Troubleshooting>
7-1
IM 21B03D01-01E
7. Troubleshooting
7.1 Overview
If the PK200 converter does not operate normally,
check the condition carefully and solve any problem
in accordance with section 7.3 Troubleshooting
Flow.
If problem appears difficult to correct, consult
YOKOGAWA service personnel.
7.2 Operation Principle
The PK200 current-to-pneumatic converter accepts
a 4 to 20mA or 10 to 50mA current signal from an
electronic controller as an operating signal. This
signal is input to a torque motor via an electric
circuit, generating a torque proportional to the
current signal.
An increase in the input signal causes the flapper at
the end of the torque motor moving piece to move
in the nozzle closing direction. When the nozzle
is closed, back pressure increases, displacing
the input diaphragm inside the control relay. This
causes the control relay output air pressure to
increase.
This output air pressure is output as PK200
converter output pressure and is also input to
a feedback pressure sensor. The sensor then
converts the pressure input into an electric signal,
which is fed back to the electric circuit. The signal is
then compared with the manipulated output signal,
the result of which activates modification action
until an output air pressure balanced with the input
signal is obtained.
In this way, an output air pressure proportional
to the input signal, which is a manipulated output
signal, is obtained.
Torque
motor
Voltage
Voltage
–
+
4 to 20mA
input
20 to 100 kPa
Output
Nozzle
flapper
Pressure
sensor
Pilot relay
Position
Air
pressure
Air
pressure
F0701.ai
Figure 7.1
PK200 Current-to-Pneumatic Converter Operation Principle Diagram
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