ABSTRACT
The accuracy of the measurement is a function of the reliability of the thermal conductivity data used for the gases making up the mixture, and those data are not always accurate. Composition measurement using the thermal conductivity properties of gases is the simplest and earliest method of process analytical instrumentation. The full span of the analyzer should correspond to a minimum of a 2% change in the thermal conductivity of the gas mixture. A thermal conductivity analyzer consists of three major components: measuring cell, regulated power supply and Wheatstone bridge, and case temperature control. Hot wire filaments are in prevalent usage following improved filament designs, but prior to 1965, thermal conductivity analyzers frequently utilized thermistors to achieve desired sensitivity. With the hardware involved defined, the operation of the thermal conductivity analyzer can be described. The advantages of the thermal conductivity analyzer include its low cost, simplicity, reliability, and reasonable speed of response.
