Patent ID: 7820949

Claim:
A method of stopping a gas sensor, the method comprising: providing a gas sensor within a wall of a flow tube in which a detection gas having a water content flows from a fuel cell, the gas sensor including: a gas detection chamber into which the detection gas is introduced; a heater which heats an interior of the gas detection chamber; and a detection element which is disposed within the gas detection chamber and thermally coupled to the heater for detecting the detection gas; providing a controller which independently controls a supply of electricity to the heater and a supply of electricity to the detection element; detecting a first temperature inside the gas detection chamber; detecting a second temperature of the detection gas discharged from the fuel cell to the gas detection chamber at a location between the fuel cell and the gas detection chamber; stopping the supply of electricity to the detection element and then controlling the supply of electricity to the heater to maintain the first temperature in a predetermined temperature range, which is higher than the second temperature, for a predetermined time; and stopping the supply of electricity to the heater after the predetermined time has elapsed, wherein the step of controlling the supply of electricity to the heater comprises: increasing the supply of electricity to the heater when a difference between the first temperature and the second temperature is less than a lower limit value; and decreasing the supply of electricity to the heater when a difference between the first temperature and the second temperature is greater than an upper limit value.