Instruction Manual
D101728X012
3710 and 3720 Positioners
September 2017
25
Calibration
The following calibration procedures are for the 3710 pneumatic positioner adjustment. For the 3720
electro‐pneumatic positioner, there are no adjustments within the 3722 converter portion of the positioner. All
adjustments are accomplished within the pneumatic portion of the positioner.
WARNING
During calibration the valve will move. To avoid personal injury or property damage caused by the release of pressure or
process fluid, provide some temporary means of control for the process.
Setting the Initial Cam Position
Before trying any calibration procedure, follow these instructions to position the cam (key 36) with respect to the valve
position.
1. Unscrew the four captive cover screws (key 8) and remove the positioner cover assembly (key 7).
2. See figure 17. Inspect the cam (key 36) and loosen the cam locknut (key 37).
3. Disconnect the positioner output tubing at the actuator and attach a regulated air source or other means of
positioning the actuator.
4. Position the
actuator
to correspond with the initial valve position at minimum instrument input signal. Stroke the
actuator to the final valve position and note the direction of actuator shaft rotation. Return the actuator to its initial
valve position.
the arrow on the cam corresponds with the direction of actuator shaft rotation for increasing input signal. Tighten
the cam locknut, leaving a gap of approximately 0.80 mm (0.031 inches) between the cam and roller. Tighten the
cam nut to 3.8 to 9.1 n
S
m (30 to 75 lbf
S
in).
6. Reconnect the output tubing to the actuator.
Figure 17. Loosening the Cam Locknut
W5916
Figure 18. Proper Cam Position
A6045
0.8 mm
(0.031 INCH)