Patent ID: 6889554
Filing Date: 2005-05-10
Classification: G01L

Abstract:
1. A method of adjusting a pressure sensor having a pressure sensitive section including a Wheatstone bridge circuit attached to a pressure application surface thereof, the pressure application surface being strained by pressure introduction of a medium to be measured, the Wheatstone bridge circuit being formed by first to fourth gauge resistances each having a resistance value varying according to an amount of strain of the pressure application surface, and an offset adjustment resistance, a temperature-compensating adjustment resistance, and a span adjustment resistance, which are attached to a non-strainable surface of the pressure sensitive section, the offset adjustment resistance and the temperature-compensating adjustment resistance being incorporated in the Wheatstone bridge circuit, the span adjustment resistance being arranged between the Wheatstone bridge circuit and a power supply, and an amplification circuit for amplifying a pressure detection signal from the pressure sensitive section, the method comprising: a measurement step of measuring a rate of change in an output voltage of the amplification circuit responsive to a change in a pressure applied to the pressure application surface, and a temperature drift of an offset voltage of the amplification circuit, the offset voltage varying in accordance with a change in an ambient temperature at atmospheric pressure, in a state of the pressure sensitive section and the amplification circuit being connected to each other; a first trimming step of calculating a first trimming resistance value based on the measured temperature drift, and trimming the temperature-compensating adjustment resistance in a manner such that the temperature-compensating adjustment resistance agrees with the first trimming resistance value; a second trimming step of calculating a second trimming resistance value based on the rate of change in the output voltage, and trimming the span adjustment resistance in a manner such that the span adjustment resistance agrees with the second trimming resistance value; and a third trimming step of trimming the offset adjustment resistance in a manner such that the output voltage on the amplification circuit side becomes equal to a desired offset voltage at atmospheric pressure.