1) Measures thermal conductivity 2) Measuring device 3) Measuring instrument 4) Measuring system 
instrument measuring changes in composition of gases
A katharometer is an instrument for comparing the thermal conductivities of two gases by comparing the rate of loss of heat from two heating coils surrounded by the gases. The instrument can be used to detect the presence of a small amount of an impurity in air and is also used as a detector in gas chromatography.
[n] - measures thermal conductivity
noun measures thermal conductivity