ABB AV1, Руководство по эксплуатации, Страница: 89 / 126

INTRODUCTION
A - 1
APPENDIX A - POSITION TRANSMITTERS
INTRODUCTION
This appendix provides operation and calibration information for
ABB position transmitter options. Refer to Table
1-4 (potentiomet-
ric position transmitter) or Table 1-5 (four to 20-milliamp position
transmitter) for position transmitter performance specifications. A
position transmitter provides additional control features to Type AV
positioners and can be ordered through nomenclature.
Position transmitters sense the position of the positioner cam
shaft. Two variations exist:
•
Potentiometric option (AV____1__).
•
4 to 20-milliamp option (AV____2__).
DESCRIPTION AND OPERATION
Position transmitters are available as options (order through
nomenclature).
The Type AV
____
1
__
potentiometric position transmitter option
uses a high durability plastic film potentiometer. Gears connect
the potentiometer 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
approximately 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 Type AV
____
2
__
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, producing 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 cur-
rent monitoring.