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Pressure Sensor Electronic Converter

IP.com Disclosure Number: IPCOM000094304D
Original Publication Date: 1966-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Collins, JA: AUTHOR [+3]

Abstract

This device provides a current output signal representative of pressure and a voltage output signal representative of temperature.

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Pressure Sensor Electronic Converter

This device provides a current output signal representative of pressure and a voltage output signal representative of temperature.

Sensor element 1 is an N-type silicon cube approximately 80 mils on a side, having four resistance elements of P-type material arranged as shown. When a force is applied to cube 1 in the direction of the arrow, the resistance elements change value in a manner which unbalances bridge 2 between points B and D. The unbalance signal is amplified by transistors Q1 and Q2. The differential output from Q1 and Q2 is converted into a single-ended signal by transistors Q3 and Q4. Stage Q5, having a load resistor 3, develops a signal proportional to the bridge unbalance. The signal across resistor 3 serves as an input to the compound connection of Q6 and Q7. Current drawn by Q6 and Q7 flows primarily through resistor 4. The resulting IR drop across resistor 4 tends to reduce the bridge error signal between points B and D.

The sensor is excited from a constant current source which includes transistors Q8 and Q9. This configuration allows the temperature-induced resistance change of the sensor elements to be sensed independently of the pressure on cube 1. Since all temperature induced resistance changes in the elements are additive, the voltage between points A and C is indicative of the sensor temperature.

Since sensors of this type are commonly used at the end of long transmission lines, current transmission...