熱線式マイクロブリッジMEMSセンサのガス検出特性 [in Japanese] Characteristics of a Microbridge-type MEMS Gas Sensor for the Thermophysical Detection by a Steady-state Hot Wire Method [in Japanese]
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Thermal conductivity <i>λ</i> of gases was measured by a steady state method using a microbridge-type MEMS sensor fabricated on a Si substrate. The sensor consisted of a hot wire with two adjacent thermocouples (TCs) on the surface of a SiO<sub>2</sub> microbridge. Due to the small heat capacity of the microbridge, the temperature after heating increased much faster to a saturated vale <i>ΔT</i> than the onset time of natural convection, enabling the <i>ΔT</i> to be used for steady-state analysis. In moving gases, the difference of the <i>ΔT</i> between the upstream and the downstream TCs was proportionally increased with the flow velocity. In static gases, this difference intrinsically became zero, and the heat flow <i>Q</i><sub>P</sub> from the hot wire to base SiO<sub>2</sub>/Si pad areas was calculated using the input heating power <i>Q</i> to yield a constant <i>ΔT</i> for a set of gases with known <i>λ</i>. Once <i>Q</i><sub>P</sub> was obtained, the <i>λ</i> of unknown gases was found to be easily estimated with errors of less than 1% by measuring the <i>Q</i> to yield the same <i>ΔT</i>.
- IEEJ Transactions on Sensors and Micromachines
IEEJ Transactions on Sensors and Micromachines 135(7), 263-268, 2015
The Institute of Electrical Engineers of Japan