Patent ID: 7794575

Claim:
A monitor for use with a 2-terminal sensor for monitoring an atmosphere for the presence of a target gas, the monitor comprising: a) two terminals for connection, respectively, to a working (sensing) electrode and a counter electrode of an electrochemical gas sensor, the sensor providing a current between the terminals that is indicative of the amount of target gas in the atmosphere, said monitor having only two contacts for connection to a 2-terminal sensor; b) an inverting operational amplifier, an inverting input of the inverting operational amplifier coupled to the working (sensing) electrode of the electrochemical gas sensor via a first pathway and a non-inverting input of the inverting operational amplifier coupled to ground to generate an output signal according to the current flowing between the terminals, whereby the output signal is indicative of the amount of target gas in the atmosphere, c) a detector for detecting when the current flowing between the sensor terminals exceeds a predetermined threshold associated with saturation of the inverting operational amplifier; and d) a circuit that restricts the potential difference between the sensor electrode terminals by detecting that the current between the terminals exceeds the predetermined threshold and by injecting additional current to or removing current from the working sensor terminal via the first pathway in order to oxidize substantially all of the target gas in contact with the working electrode until the inverting operational amplifier is no longer saturated.