Cameron BARTON 764 - Section 2: Internal Circuitry; Electronic Transmitter Circuit Stages; Factory Temperature Compensation

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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 amplier stage, and provides stabilized voltage for
bridge excitation and power for the signal amplier.
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 Amplier
The signal amplier is an integrated circuit operational amplier which pro-
vides amplication of the strain gage bridge network output voltage.
Current Amplier
The current amplier circuit converts the signal amplier 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
eld without voiding the qualications certication.
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.