Search

The thermoelectric hydrogen (H2) gas sensor using PCB (Printed Circuit Board) technique was developed based on the exothermic absorption of H2 by a palladium (Pd) film coated on a thermocouple. A cascade connection of two thermocouples composed of copper (Cu) and constantan (55% nickel and 45% Cu) was used to detect the exothermic absorption of H2 by Pd. The differential thermoelectric voltage output between the two thermocouples (with and without the Pd film) increased linearly with the H2 gas concentration in a 2.0–50 vol% ambient atmosphere. Standard deviations (SD) for 8 measurement cycles are typically 1.1% at 4 vol% H2, 0.81% at 6 vol% H2, and 1.9% at 8 vol% H2, respectively. The differential thermoelectric voltage output can be detected from 2.0 vol% H2 atmosphere. The ambient temperature fluctuations on the measurement was also effectively reduced using the cascade connection of two thermocouples. Calibration line of H2 concentration calculated by the least square method is linear and standard error (SE), 0.44 vol%, is smaller than measured value.

A fluorescent temperature sensor using temperature dependence of fluorescent inorganic materials is studied for low temperature measurement. Ruby (chromium ions doped sapphire) is used as a sensor head of the fluorescence thermometer because of long photoluminescence (PL) lifetime and visible emission. In this research, ruby crystal is found to be useful as the sensor head for fluorescence thermometer. In addition, the ruby crystal is potentially useful material for the sensor head crystals to measure low temperature below 0 °C.