 However, If the dissimilar gas sample (or gas mixture) is passed over one set of two filaments and the reference gas on the other set of two filaments, then the Wheatstone bridge becomes unbalanced.And the resulting net voltage output of the circuit will be correlated with the database to identify the constituents of the sample gas.Using this technique many unknown gas samples can be identified by comparing their thermal conductivity with other reference gas of known thermal conductivity.