Abstract
A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Qcatalyst required for 1 mV of ΔVgas was calculated to be 46.1 μW. Using these parameters, we find from simulations for the device performance that the expected Qcatalyst for 200 and 1,000 ppm H2 was 3.69 μW and 11.7 μW, respectively.
Highlights
Inflammable gases such as CO, CH4, and H2, which can amount to several hundred parts per million in human breath [1,2], can be used for medical examination and detected by the micro-calorimetric device of a thermoelectric gas sensor (TGS) with a combustion catalyst
We have reported that a TGS with a Pt-loaded alumina (40 wt%Pt/alumina) catalyst can detect H2 over a wide concentration range from as low as 0.5 ppm up to 5 vol.% H2 in air [3]
Additional improvements in the TGS device are required for the detection of CO and CH4, such as much higher catalyst temperature and precise temperature control, because CO and CH4 are less inflammable as compared to H2
Summary
Inflammable gases such as CO, CH4, and H2, which can amount to several hundred parts per million in human breath [1,2], can be used for medical examination and detected by the micro-calorimetric device of a thermoelectric gas sensor (TGS) with a combustion catalyst. We have reported that a TGS with a Pt-loaded alumina (40 wt%Pt/alumina) catalyst can detect H2 over a wide concentration range from as low as 0.5 ppm up to 5 vol.% H2 in air [3] This device showed a good linearity between the H2 concentration in air and the sensing signal at the catalyst temperature of 100 °C. The heat of combustion of the small amount catalyst which is used for gas sensors is difficult to estimate since it is difficult to measure the temperature of small parts of devices like sensors. Calculations for the rate of catalytic combustion converted to a voltage signal using a heat balance calculation are compared with the experimental results that estimate the rate of catalytic combustion of a TE hydrogen sensor
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