ABB AV2123000 Positioner User Manual

POSITION TRANSMITTERS
tolerance of the potentiometer. Figure A-2 is a schematic diagram
of this application example.
2000 Ω ±20%
200-912.8Ω
TB1
1 2 3 4 5
+
OUTPUT
–
2380Ω
NOMINAL
ADJUSTMENT
–
24 VDC
+
T00787A
Figure A-2. Schematic Diagram
CALIBRATING THE POTENTIOMETRIC EXAMPLE
The calibration information is based on the application put forth in
POTENTIOMETRIC APPLICATION EXAMPLE.
1. Move the actuator to the 0% output position.
2. Remove the field wiring from TB1-1, TB1-2 and TB1-3. Using
an ohmmeter, measure the resistance between TB1-1 and TB1-2.
If the reading is 200, ±20 Ω, remove the ohmmeter and proceed to
Step 3. Otherwise continue with Step 2.
WARNING
The pneumatic supply pressure must be turned off before
removing the positioning cam. The final control element will
go to one end of the stroke and can cause a process upset.
Some process upsets may cause damage to equipment and
endanger personnel.
a. Remove the cam by removing the screw, flag, nut and
washer (Fig. A-3 and Table A-1).
b. Loosen the set screw on the hub of the small gear using a
1⁄
16 -in. Allen wrench (Fig. A-3 and Table A-1).
c. Use a screwdriver to adjust the shaft on the potentiometer
until the ohmmeter reads 200, ±20 Ω. While adjusting the
resistance, hold the gears and cam shaft stationary so rotation
does not occur. Only the potentiometer shaft should move
while adjusting the resistance.
CALIBRATION
A - 4