Patent ID: 8410801

Claim:
A pressure detection apparatus comprising: a pressure-sensitive resistor whose first resistance r 1 varies according to a change of a pressure P, which is an object of detection, and a change of a temperature T of the pressure-sensitive resistor itself; a temperature-sensitive resistor which has a same resistance-temperature coefficient as the pressure-sensitive resistor and whose second resistance r 2 varies according to the change of the temperature T; wherein one end of the pressure-sensitive resistor and one end of the temperature-sensitive resistor are connected to the first constant-current source and the second constant-current source respectively, and the other end of the pressure-sensitive resistor and the other end of the temperature-sensitive resistor are connected to each other; a current source for supplying a current to the pressure-sensitive resistor and the temperature sensitive resistor, the current source having a first constant-current source that supplies a predetermined first constant current i 1 to the pressure-sensitive resistor, and a second constant-current source that supplies a predetermined second constant-current i 2 to the temperature-sensitive resistor, and the current source adjusting magnitudes of the predetermined first constant-current i 1 and the predetermined second constant-current i 2 so that when the pressure P is an initial pressure P o , a reference first voltage V po that appears across the pressure-sensitive resistor and a reference second voltage V to that appears across the temperature sensitive resistor become equal to each other; and a pressure signal generation output section which generates and outputs a first voltage signal S pp corresponding to the pressure P on the basis of a difference voltage (V p -V t ) between a first voltage V p that appears across the pressure-sensitive resistor in accordance with the pressure P and a second voltage V t that appears across the temperature-sensitive resistor.