Method of measuring an air to fuel ratio.

摘要

The air-to-fuel ratio of an air/fuel mixture being supplied to a combustion process is determined by establishing an oxygen sensor station (12) at which the sensor senses the difference in oxygen partial pressure from a first reference side thereof to a second oxygen measurement side thereof. The oxygen sensor is maintained at a predetermined temperature and at a pressure below atmospheric pressure. The oxygen sensor is calibrated so that the measurement thereby of an EMF between the first reference side thereof and the second oxygen measurement side thereof is indicative of the oxygen partial pressure in a gas stream passing by the oxygen measurement side thereof. A sample gas stream (24) is drawn across the second oxygen measurement side of the oxygen sensor at a pressure which allows samples to be drawn at a constant flow rate independent of that pressure. A fixed amount of oxygen (26) is added to the sample gas stream. The oxygen in the sample gas stream is reacted with oxidisable species contained in the sample gas stream prior to passing the sample gas stream across the second oxygen measurement side of the oxygen sensor (12). The pressure of the gas sample is measured. The air to fuel ratio of the air/fuel mixture is determined from the measured EMF of the oxygen sensor, the total pressure of the sample gas stream and the known oxygen addition rate. Suitable oxygen sensors may be formed zirconia or titania.