Extremely simple structure hydrogen gas sensor based on single metallic thin-wire under sweep heating

Abstract

We here propose a sweep heating of a single metallic thin-wire for thermal conductivity detector (TCD)-based gas sensor. Owing to the sweep heating, much information can be acquired compared with the typical heating. Accordingly, even though the sensing element is only the single metallic thin-wire, it can detect hydrogen without the compensator. After the simple mathematical operation, the relation between input power (P) and resistance (R), namely P-R diagram, can be calculated and it depicts a change in thermal conductivity of surrounding gas clearly. Indeed, hydrogen gas over a wide range of concentrations from 1 to 100%H2 can be detected via a slope and hysteresis area of the diagram. The sensor response was stable and related almost to an inverse of thermal conductivity of gas. The observed temperature increase during the sweep heating shows a good agreement with a temperature profile calculated from finite element method (FEM). Therefore, the sensor temperature represents the thermal conductivity of gas, although the sweep heating works under non-equilibrium state. From a comparison between platinum, tungsten and cobalt thin-wires, it was confirmed that any metal can be employed for sensing element of this sensor. The proposed sweep heating thin-wire gas sensor is a cost-effective and expected to be suitable for practical use in harsh environment such as automotive applications because of its simple structure and simple working principle. The sweep heating expands diversity on TCD-based gas sensor and contributes to realizing the sustainable development goals (SDGs).