Patent ID: 8232813

Claim:
A circuit for operating a first amperometric sensor and a second amperometric sensor, each having a reference electrode, a counter electrode and a work electrode, wherein the first amperometric sensor is configured to operate at a positive work potential and the second amperometric sensor is configured to operate at a negative work potential, the circuit comprising: an amplifier having a positive input and a negative input and an output, the positive input being coupled to a single reference voltage source for outputting a settable single positive reference voltage, and the negative input and the output being coupled together via a negative feedback loop; a subtractor within said negative feedback loop and having an output coupled to the negative input of the amplifier; switching means which when set in a first configuration causes the single reference voltage source to positively bias the first amperometric sensor with a positive work potential by coupling the first amperometric sensor into said negative feedback loop of the amplifier such that the counter electrode of the first sensor is coupled to said output, a positive input of the subtractor is coupled to the reference electrode of the first sensor, and a negative input of the subtractor is coupled to the work electrode of the first sensor, and which when set in a second configuration causes the single reference voltage source to negatively bias the second amperometric sensor with a negative work potential by coupling the second amperometric sensor into said negative feedback loop such that the work electrode of the second sensor is coupled to said output, the positive input of the subtractor is coupled to the work electrode of the second sensor, and the negative input of the subtractor is coupled to the reference electrode of the second sensor.