Flowserve PMV D3 Digital Positioner - Manual (Page 7)

7
5. Function
Control signal 4 - 20 mA
Potentiometer
Piezo-valve 1 Piezo-valve 2
Diaphragm
Pressure
regulator
Replaceable
Filter
Air supply 2 - 6 bar
1.2 bar
Venting
Venting
H
G
Double action function
The control signal and the feedback
potentiometer position are converted to di-
gital signals that are processed with a PID
algorithm in the microprocessor. This prov-
ides control signals to the two piezo-valves.
The two piezo-valves are closed in the
schematic diagram above and have no effect
on the valves A and D. Air from the pressure
regulator is lead through the open valve A to
the valve B, which opens. The supply
pressure can now pass through valve B to
the actuator via H. The actuator then moves
in the direction of the arrow. At the same
Signal converter
and
microprocessor
A B
C
D
E
F
➾
time, air from valve A keeps valve C open
and allows venting of the actuator.
When both the piezo-valves open, valve
A closes but valve D opens and controls
valves E and F to that the actuator moves in
a direction opposite to the arrow. When only
piezo-valve 1 is open, the actuator is
stationary.
Single action function
Valve B is used for the supply air and
valve F for venting.
C– C+
Actuator