Potentiometric Application Example; Calibrating The Potentiometric Example - ABB AV1 Operating Instructions Manual

POSITION TRANSMITTERS
WARNING
CALIBRATION
A - 4
tolerance of the potentiometer. Figure
of this application example.
Ω
2000
200-912.8Ω
1 2
TB1
Figure A-2. Schematic Diagram

CALIBRATING THE POTENTIOMETRIC EXAMPLE

The calibration information is based on the application put forth in
POTENTIOMETRIC APPLICATION
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.
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
⁄
-in. Allen wrench (Fig.
1
16
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.
A-2 is a schematic diagram
±20%
3 4 5
2380
+
NOMINAL
OUTPUT
ADJUSTMENT
–
– +
24 VDC
EXAMPLE.
A-3 and Table A-1).
Ω
T00787A