Appendix A - Position Transmitters; Introduction; Description And Operation; Potentiometric Position Transmitter - ABB AV3 Instruction Manual

INTRODUCTION

DESCRIPTION AND OPERATION

Potentiometric Position Transmitter

Four to 20 mA Position Transmitter

APPENDIX A - POSITION TRANSMITTERS

This appendix provides operation and calibration information for ABB
position transmitter options. Refer to Table
tion transmitter) or 1-5
position transmitter performance specifications. A position transmitter
provides additional control features to Type AV positioners.
Position transmitters sense the position of positioner cam shaft. Two
variations exist:
Potentiometric option (AV
•
Four to 20 mA option (AV
•
This is available as an option for the Type AV3 positioner (order
through nomenclature). The potentiometric option is not available for
the Type AV4 positioner.
The potentiometric position transmitter option (AV33
high durability plastic film potentiometer. Gears connect the potenti-
ometer to the positioner cam shaft. The position of the potentiometer
shaft indicates the position of the actuator.
The relationship between the potentiometer and the cam shaft results
in one degree of rotation of the cam shaft corresponding to approxi-
mately 9.9 ohms of resistive change at the potentiometer wiper.
Three leads from the potentiometer are for customer use and are
available at terminals TB1-1, TB1-2, and TB1-3.
The four to 20 milliamp position transmitter option also uses a high
durability plastic film potentiometer and electronic circuitry. Gears
connect the potentiometer shaft to the positioner cam shaft. The
resistive change of the potentiometer outputs to a bridge circuit, pro-
ducing a proportional voltage. EMI/RFI protected circuitry converts
the bridge voltage to a four to 20 milliamp current signal. Terminals
TB1-1 (+) and TB1-2 (-) of the Type AV positioner provide customer
access to the four to 20 milliamp control signal. Jumper position
determines direct or reverse-acting operation. Test jacks are available
for in line current monitoring.
1-4
(four to 20 milliamp position transmitter) for
1 ).
2 ).
(potentiometric posi-
1 ) uses a
INTRODUCTION
A - 1