Patent ID: 7532010

Claim:
A sensing circuit for detecting open and short circuit conditions in a sensor, comprising: switching circuitry electrically coupled to a sensor having a sensor capacitance; a voltage supply electrically coupled to said switching circuitry; a test capacitor coupled to said switching circuitry and having a test capacitance; an operational amplifier having inputs and at least one output said operational amplifier being electrically coupled to said switching circuitry, wherein said sensing circuit is configured to provide for a normal operating mode in which said switching circuitry electrically couples the sensor to said voltage supply and said operational amplifier such that the output of said operational amplifier is indicative of the voltage across the sensor, and wherein said sensing circuit is further configured to provide for a charging mode in which said switching circuitry electrically couples said voltage supply to said operational amplifier, and electrically couples said test capacitor to said operational amplifier and the sensor, such that the output voltage of said operational amplifier is a function of the voltage provided by said voltage supply and a ratio of the test capacitor capacitance to the sensor capacitance; and analysis circuitry coupled to the output of said operational amplifier, wherein said analysis circuitry is configured to monitor the output voltage by said operational amplifier and determine, based on the monitored voltage, if the sensor is in one of an open-circuit condition, a short-circuit condition, a shorted to battery condition, a shorted to ground condition, and a normal operating condition.