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Section 2
Model 764 Differential Pressure Transmitter
Regulator
This stage of the circuit regulates that portion of the loop current which is not
calibrated at the current amplifier stage, and provides stabilized voltage for
bridge excitation and power for the signal amplifier.
Strain Gage Bridge Network
The strain gage bridge network consists of two silicone piezo-resistive strain
sensors, the zero adjusting potentiometer, bridge completion resistors, and the
temperature compensation components.
Signal Amplifier
The signal amplifier is an integrated circuit operational amplifier which pro
-
vides amplification of the strain gage bridge network output voltage.
Current Amplifier
The current amplifier circuit converts the signal amplifier output voltage to
current. The amount of current is precisely regulated with the feedback net-
work to make it proportional to the bridge output.
Temperature Compensation
The Model 764 transmitter is temperature-compensated at the factory. Only
those repairs described in Section 4 of this manual may be performed in the
field without voiding the qualifications certification.
IMPORTANT: Combined zero and/or span changes more than ±5% of the factory
calibration can adversely impact transmitter performance. The transmitter
performance may be decreased in direct proportion to the changes to the
factory calibration. If the combined zero and/or span changes represent
a change in the factory calibration by a factor of 2, the transmitter perfor-
mance may be decreased by a factor of 2.
