Burns, Doane, Swecker & Mathis
Fault detector for an air bag system
 A fault of a trigger resistor or a squib resistor of an air bag system is monitored together with other resistors by utilizing a balanced Wheatstone bridge for providing an inexpensive and highly reliable fault detector, wherein first and second junctions of the Wheatstone bridge are connected alternately to a dc amplifier circuit with use of first and second switching circuits for applying a voltage across the squib resistor and a reference voltage alternately on an input terminal of the dc amplifier circuit, amplified voltages are fed from the dc amplifier circuit to a decision circuit to check whether or not the voltage across the squib resistor is within an allowable limit from the reference voltage, the amplified reference voltage is fed from the dc amplifier circuit to a voltage regulating circuit, which has a feedback circuit to the dc amplifier circuit, with use of a third switching circuit for adjusting an output of the voltage regulator to the center value of the input voltage range of the decision circuit, and thereby making it possible to measure a voltage difference at the first and second junctions without being influenced by a fluctuation of the supply voltage or a change of resistance ratio of acceleration sensors. 
Mitsubishi Denki Kabushiki Kaisha
G B G
G01R B60R G01R
inventional inventional inventional
Takashi Hisatsugu
Furui Ito