Calibrate The Potentiometric Application Example - ABB AV3 Instruction Manual

POSITION TRANSMITTERS
WARNING
CALIBRATION
A - 4
6. Determine the dropping resistor value which reduces the supply
voltage to 10.96 VDC:
24 VDC 10.96 VDC
–
-------------------------------------------------------- -
5.48 mA
Connect a 2380 ohm variable resistor in series with the power supply.
A variable resistor is required to account for the 20-percent tolerance
of the potentiometer. Figure
cation example.
Ω
200 0 ± 20%
200 -9 12.8 Ω
1 2
TB 1
+
–
Figure A-2. Schematic for Potentiometric Position

CALIBRATE THE POTENTIOMETRIC APPLICATION EXAMPLE

T he calibrating information that follows 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 ohms, 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 endan-
ger personnel.
2380Ω
=
A-2 is a schematic diagram of this appli-
3 4 5
O U T P U T
– +
24 V D C
Transmitter Example
Ω
238 0
N O M IN A L
AD JU S T M EN T
T 00 7 87 A