5
Model 764 Differential Pressure Transmitter
Section 1
Section 1—Introduction
General
The Model 764 Differential Pressure Transmitter provides a 4-20 mA or 10-
50 mA proportional-to-differential pressure signal for transmission to remote
receiving, control, or readout devices.
The electronic components of the Model 764 transmitter are housed in a
pressure-sealed enclosure. The instruments are designed to operate beyond
their normal operating environmental specifications for a limited period of
time under such adverse conditions as may be encountered within the contain
-
ment of a nuclear power plant under accident and post-accident conditions.
These adverse environments include severe changes in ambient pressure,
temperature and humidity, seismic events, and radiation exposure.
Product Description
The Model 764 transmitter combines a differential pressure unit (DPU) with
an electronic circuit. The 4-20 mA or 10-50 mA output is compatible with a
wide range of electronic receiving, control, and readout equipment. The in
-
strument utilizes electronic circuits and a molecular-bonded strain gage sens-
ing cantilever beam, actuated directly by the bellows travel within the DPU.
Differential Pressure Unit (DPU)
The mechanical actuating device for the Model 764 transmitter is a dual
bellows assembly enclosed by a set of two pressure housings. The dual bel-
lows assembly (Figure 2.1,
page 9
) consists of two internally-connected
bellows, a center block, overrange valves, a temperature compensator, a strain
gage assembly, and range springs. The internal volume of the bellows and
center block is completely filled with a clean, non-corrosive, non-conductive
liquid with a low freezing point and sealed. The motion-sensing cantilever
beam is also sealed within this environment.
Electronic Transmitter
The electronic transmitter supplies either a 4-20 mA or 10-50 mA direct cur
-
rent output signal that is proportional to the differential pressure sensed by the
DPU. The output signal is transmitted over a two-wire transmission line to
remote receiving devices.
Power Supply
A regulated direct current (DC) power supply is required to operate the trans
-
mitting loop.
