Patent ID: 7849726

Claim:
A gas chromatograph for connection to a source of carrier gas and a source of a sample gas and operable to analyze the sample gas, the gas chromatograph comprising: a carrier gas line for carrying the carrier gas; a reference sensor connected into the carrier gas line, the reference sensor having a resistance that is dependant on the temperature of the reference sensor; a sample inlet line for carrying the sample gas; a valve connected to the carrier line and the sample inlet line and operable to inject the sample gas into the carrier gas; a separation device connected to the valve to receive the carrier gas with the sample gas and operable to separate components of the sample gas; a sample outlet line connected to an output of the separation device to receive the carrier gas and the separated components of the sample gas; a sample sensor connected into the sample outlet line, the sample sensor having a resistance that is dependant on the temperature of the sample sensor; a first bridge circuit comprising the sample sensor and a plurality of resistors; a first analog-to-digital converter connected to an output of the first bridge circuit and operable to generate a digitized sample signal attributable to the thermal conductivity of the carrier gas together with the thermal conductivities of the components of the sample gas; a second bridge circuit comprising the reference sensor and a plurality of resistors; a second analog-to-digital converter connected to an output of the second bridge circuit and operable to generate a digitized reference signal attributable to the thermal conductivity of the carrier gas; a processor connected to the first and second analog-to-digital converters and operable to receive the digitized sample signal and the digitized reference signal; computer readable medium; and program instructions stored on the computer readable medium and executable by the processor to subtract the digitized reference signal from the digitized sample signal to generate data attributable to the thermal conductivities of the components of the sample gas exclusive of the thermal conductivity of the carrier gas.