OVEN EXHAUST GAS OXYGEN SENSING ARRANGEMENT AND RELATED CONTROL CIRCUIT AND METHOD

An oxygen sensing arrangement for a gas-fired oven includes an oxygen sensor positioned for sensing gases along an exhaust path of the oven, the oxygen sensor including a heater and a measurement cell. A sensor control circuit includes a sensor initialization portion connected to a bridge portion. The bridge portion is operatively connected for energizing the heater. The sensor initialization portion produces a start signal which unbalances the bridge circuit for a start-up time period, causing the bridge circuit to deliver a heating current/voltage to the heater for the start-up time period . After the start-up time period the sensor initialization portion no longer produces the start signal and the bridge circuit balances so as to deliver an operating current/voltage to the heater . A voltage of the heating current/voltage is less than a voltage of the operating current/voltage. The arrangement enables the oxygen sensor to be heated to its operating temperature at a voltage and corresponding heating rate which will not damage the sensor, and is particularly useful where the oxygen sensor is an amperometric type sensor. The sensor may be located in a sensor chamber is positioned alongside the exhaust duct so as to be spaced from a primary flow of exhaust gases, with the chamber open to receive gases in the exhaust duct. Both the sensor chamber and oxygen sensor therein are sealed off from gases outside o f the exhaust duct.