Setting The Potentiometer; Calibrating The Servo - Johnson Controls VA-9070 Series Technical Bulletin

3. Loosen the cam locking screw shown in Figure 6.
Note: It is possible that the rotation of one cam may move the other cam. If this
occurs, hold the other knobs or cams during adjustment.
4. Rotate the red cam adjustment knob by hand or with a flat head screwdriver
until the red cam lobe just activates (depresses) the 'closed' switch from a
clockwise direction.
Note: If fixed auxiliary switches are installed, the auxiliary cam activates prior to
the main cam.
5. Tighten the cam locking screw.
6. Manually operate the actuator counterclockwise until the valve reaches the
desired open position.
7. Loosen the cam locking screw.
8. Rotate the green cam adjustment knob until the green cam lobe activates
(depresses) the open switch from a counterclockwise direction.
9. Tighten the cam locking screw.
10. Place the indicator rotor back on the indicator shaft.

Setting the Potentiometer

1. Manually operate the actuator handwheel until the unit is in the fully closed
position.
2. Rotate the black potentiometer drive gear adjustment knob to barely engage the
potentiometer gear segment at the closed position.
3. Manually operate the actuator to the fully open position.
4. Fine-tune the potentiometer adjustment at this end to equalize the difference
between the ends. The potentiometer gear segment should maintain
engagement with the drive gear throughout full actuator travel.

Calibrating the Servo

Note: The Servo NXT is not remotely controllable during the autocalibration
sequence. If autocalibration needs to be aborted, pull the handwheel.
Autocalibration mode is entered by pressing and holding the Autocalibration
button for at least three seconds. Entering Autocalibration mode starts the
autocalibration sequence: a series of commands performed by Servo NXT on the
actuator to determine the operating points. During the autocalibration sequence,
the Servo NXT should be monitored to ensure it operates correctly. The product
settings' indicators change state to show that autocalibration has been entered, and
continue to flash at the end of travel until autocalibration completes. Upon
completion of the autocalibration sequence, the product settings' indicators return
to normal.
10 VA-9070 Series Electric Rotary Actuators for Two-Position and Modulating Service Technical Bulletin