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Abstract

A pressure transducer of the type employing a pressure-responsive diaphragm (11) with silicon piezoresistive strain gauges epitaxially deposited thereon is provided with integral digital thermal compensation of span shift and zero shift. The strain gauges are connected in a bridge circuit (30), and a differential voltage across the bridge circuit is amplified by an instrumentation amplifier (46). A temperature sensitive resistor (36) is deposited on the pressure-responsive diaphragm. This resistor is connected in a bridge circuit (35) the output of which is connected to an analog-to-digital (A/D) converter (54) which generates a digital number corresponding to the measured temperature of the piezoresistive strain gauges. This digital number is used to address pre-programmed correction data stored in a programmable read only memory (PROM) (53). The numerical correction data from the PROM is converted by a digital-to-analog (D/A) converter (55) to an analog correction signal. The D/A converter has two outputs which are alternately selected by a timing and control circuit (56) to provide thermal span shift and thermal zero shift correction signals. The thermal span shift signal is used to modify the excitation voltage of the piezoresistive strain gauge bridge circuit, while the thermal zero shift signal is added to the amplified voltage output of the bridge circuit. A simple analog circuit (58) provides linearity compensation.

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