Zero Adjustment (Av4) - ABB AV3 Instruction Manual

CALIBRATION
GENERAL CALIBRATION
4 - 4
not move until another pulse is provided to either the raise or
lower terminals.
Calibrating a Type AV4 positioner consists of the following adjust-
ments:
Zero.
•
Span.
•
Motor speed adjustment.
•
The Type AV4 positioner has a four to 20 milliamp position trans-
mitter that provides feedback to the controller. The feedback sig-
nal is proportional to the position of the cam. Refer to
for more information about the position transmitters.

ZERO ADJUSTMENT (AV4)

Setting the zero requires the alignment of the zero percent radial
line of the cam with the center of the cam roller. Use the following
steps to adjust the zero.
1. Pulse the lower (TB1-5) terminal of the positioner in order to
arrive at the minimum internal signal of 20.0, ±1.4 kPa (3.0, ±0.2
psi). The internal signal pressure may be measured at port I.
2. Loosen the zero adjustment set screw (Fig. 4-1) using
⁄
-inch Allen wrench.
3
32
3. Turn the zero adjustment nut (clockwise moves actuator down
range) appropriately until the actuator moves so that the 0% radial
line on the cam intersects with the center of the cam roller (Fig.
4-2).
NOTE: This adjustment may be biased, i.e. turning the zero nut
slightly counterclockwise to make sure a valve or damper is
firmly seated at the minimum input signal.
4. Tighten the zero adjustment set screw.
SPAN ADJUSTMENT (AV4)
Setting the span requires the alignment of the 100 percent radial
line of the cam with the center of the cam roller. Use the following
steps to adjust the span.
1. Pulse the raise (TB1-4) terminal until the actuator reaches the
maximum position.
2. Loosen the span adjustment screw with a
wrench.
Appendix A
⁄
-inch Allen
5 32