User instructions - Digital Positioner 3200MD LGENIM0059-01 10/08
26
8.6 Stem Position Sensor
The position feedback assembly transmits valve positions informa-
tion to the processor. This is accomplished by means of a rotary
position sensor that connects to the valve stem through a feedback
linkage. To provide for accurate tracking of the pin in the slot, the
follower arm is biased against one side of the slot with a rotary
spring. This spring also automatically moves the position feedback
assembly to its limit in the unlikely event of failure of any component
in the linkage.
Stem Position Sensor Replacement
To replace the stem position sensor, refer to Figure 15, 18 and 25
and proceed as outlined below. The following tools are required:
• Phillipsscrewdriver
c
WARNING: Observe precautions for handling electrostati-
cally sensitive devices.
1. Make sure the valve is bypassed or in a safe condition.
2. Disconnect the power and air supply to the unit.
3. Remove the main cover.
4. Remove the plastic board cover by removing the three retaining
screws (see Figure 15).
5. Disconnect the position sensor wires from the main PCB
assembly.
6. Remove the two rotary position sensor-retaining screws and lift
the sensor out of the housing.
7. Turn the new position sensor shaft until the dot on the side of
the shaft is aligned with the wires on the side of the position
sensor (Figure 18).
8. Insert the position sensor into the shaft with the wires pointing
toward the main PCB assembly. Turn the position sensor clock-
Figure 18: Stem Position Sensor Orientation
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