
Limitorque L120-85 Installation, Operation and Maintenance FCD LMENIM1202-03-A4 – 06/15
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4.5.3 Setting the Potentiometer
If your L120-85 actuator includes a Feedback Potentiometer supplied for remote valve position indication, use an ohmmeter to calibrate
the position of the Potentiometer. Typically, the Potentiometer Spur Gear is shipped from the factory dis-engaged from the Potentiometer
Drive Gear. If your supplier has not re-engaged and calibrated the Potentiometer, use the following procedure to complete the Potentiometer
setup.
c
WARNING:
Hazardous Voltage. Turn power OFF before opening the Electrical Compartment Cover or calibrating the Feedback
Potentiometer. Use extreme caution if the power is ON and the Electrical Compartment is OPEN.
1. Turn all power to the actuator OFF.
2. Using the Handwheel, position the actuator to mid-travel (valve at the 50% position).
3. Disconnect the Potentiometer Wiring Harness from the Interconnect Board or Terminal Strip.
4. Using an ohmmeter, verify that the potentiometer is in mid-travel. The resistance from each End Connection to the Center Connection
should be half of the full resistance of the Potentiometer. Example: a 1000 ohm potentiometer should read approximately 500 ohms
from one of the End Connections to the Center Connection. If the reading is not correct, proceed to step 5. If the reading is correct
proceed to step 11.
Figure 15: Potentiometer Calibration configuration
Pot Lead
End Connection
Pot Lead
Center Connection
Ohmmeter
5. If the Potentiometer Assembly is engaged with the Potentiometer Drive Gear: Loosen the Hex Head Retaining Nut at the base of
the Potentiometer Bracket and dis-engage the Spur Gear from the Potentiometer Drive Gear. This will allow manual rotation of the
Potentiometer Spur Gear. Continue to step 7.