semiconductor barometer

0 vacuum © Wheatstone-bridge INEEK X = 8 V A Wheatstone bridge consisting of four piezo-resistive elements has been diffused onto the top section. When the base is bent, the bridge becomes unbalanced. Figure 2 gives the circuit diagram of the electronic barometer. When the air pressure rises, the resistance of RA and RC will drop and the value of RB and RD will increase. The supply voltage for the bridge circuit is derived from an LM 10 IC which contains a voltage reference source. The output voltage from the bridge is buffered by the opamp also contained in the LM 10. The voltage is measured by means of a digital voltmeter constructed according to a standard design. The reference voltage for the voltmeter is also derived from the LM 10. One great advantage that this electronic barometer has over its numerous semi-electronic counter- parts is that it is very easily 5V calibrated. All that is required is to measure the air pressure once with an ordinary, mechanical barometer and a...