Patent ID: 7398681

Claim:
A gas sensor comprising: a sample chamber for holding a gas sample; a sealable vacuum port in fluid communication with the sample chamber, for evacuating said sample chamber; a sealable inlet port in fluid communication with the sample chamber, for introducing the gas sample into the evacuated sample chamber; a sample control valve connected to the inlet port, for controlling entry of the gas sample into the sample chamber; and a thermal conductivity sensing element at least partly disposed within the sample chamber spaced from the inlet port for measuring the thermal conductivity of the gas sample; a controller connected to the sample control valve to open the sample control valve and connected to the thermal conductivity sensing element for detecting a change in resistance of the thermal conductivity sensing element to detect initial reaction of the thermal conductivity sensing element to the gas sample, the controller determining the time from opening the sample control valve to initial reaction of the thermal conductivity sensing element to the gas sample to thereby provide a measure of the gas sample speed.