A new type of catalytic oxygen sensor based on the measurement of hydrogen–oxygen reaction heat

A new type of catalytic oxygen sensor based on the measurement of the hydrogen–oxygen reaction heat has been constructed and evaluated. The sensor consists of thin-film platinum resistors, which constituted a Wheatstone bridge circuit, a reaction cell containing catalyst particles, a reference cell containing inert packing material, hydrogen diffusing membrane assembly, and an isothermal block. The heat liberated by the reaction increases the temperature of the reaction cell, causing an increase of resistance of the Pt resistor, and as a result, the bridge circuit produces an output signal. The reference cell and the isothermal block used reduce the influence of fluctuation of temperature and pressure of the sample gas on the base line signal. The signal of the sensor is proportional to the concentration of oxygen in the range of 1–1200 ppm. The lowest detection limit is 1 ppm. The 90% response time of the sensor is less than 5 s. The sensor is characteristic of excellent signal stability, fast response speed and high sensitivity.