Gas micro-flow-metering with the in-channel Pt resistors

Abstract

Standard thermo-conductive gas flow meters have the side-channel integrated with the temperature detector and heater coils, both winded around the tube. This design suffers from a high thermal capacity, reduced sensitivity in the lower limit flow range, high thermal inertia, long response time and necessity to amplify electronically the output signal. The newly designed TCD detector can be applied as a precise gas flow meter. To identify the composition of the unknown gas, the TCD unit requires a connection to the separation column, application of the reference channel and highly stable flow rate regulator. To measure flow rates, the same TCD unit requires only one flow channel application, with active resistors inside it, and a definition of the gas type. In this work principles of the TCD design, technology and flow rate sensitivity tests are presented.