Abstract. Hydrogen concentration measurements were developed for a series of experiments in which a molten oxide is mixed with water to study vapour explosion phenomena. The gas mixture to be analysed consisted of hydrogen with water vapour and either helium or argon. Two types of sensor have been developed for these tests. The first is an ultrasonic sensor, which detects variations in the acoustic velocity within a 0.4 mm-diameter palladium wire. The sensor measures hydrogen concentrations in the range 0.1-100%, at atmospheric pressure, over an operating temperature range of 200-400 °C. The response time (for 0-90% of the final response) is about 30 s at 180 °C and 8 s at 380 °C. The second sensor consists of a palladium coil, constructed with 0.05 mm-diameter wire that is wound around a ceramic tube. Measurements of wire resistance were used to detect partial pressure of hydrogen. This sensor operates at 150-300 °C and measures hydrogen concentrations of 1-100%. The response time is short, 1-2 s for a temperature of 300 °C.

Keywords: hydrogen sensor, ultrasonic, resistive, palladium, high temperature, inert gas

Print publication: Issue 5 (May 2000)
Received 4 January 2000, in final form and accepted for publication 29 February 2000