Setting The Potentiometer - Johnson Controls VA-9070 Series Technical Bulletin

Setting Travel Limit Switches
If the unit came assembled to a valve, the switches have been factory-set and DO NOT need
adjustment. Johnson Controls uses cam design along with 2 SPDT mechanical switches to set the
open and closed position of the valve. The green cam actuates the open switch when the actuator
reaches the open position.
Similarly, the red cam actuates the 'closed' switch when the actuator reaches the 'closed' position.
Standard factory setting of the travel limit switches means 90° travel between open and close
positions. Cams for each switch are adjustable for applications where less than 90-degree travel is
desired between the open and closed positions.
Complete the following procedure to adjust the travel limit cams.
Note: For Housing Size 130, 180, ignore steps 1 and 10.
1. Remove the indicator rotor by pulling away from the indicator shaft as shown in Figure 6.
2. Manually operate the actuator clockwise until the valve reaches the desired closed position.
3. Loosen the cam locking screw shown in Figure 8.
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
8 VA-9070 Series Electric Rotary Actuators for Two-Position and Modulating Service Technical Bulletin