Abstract
A reduced size thermocatalytic gas sensor was developed for the detection of methane over the 20% of the explosive concentration. The sensor chip is formed from two membranes with a 150 µm diameter heated area in their centers and covered with highly dispersed nano-sized catalyst and inert reference, respectively. The power dissipation of the chip is well below 70 mW at the 530 °C maximum operation temperature. The chip is mounted in a novel surface mounted metal-ceramic sensor package in the form-factor of SOT-89. The sensitivity of the device is 10 mV/v%, whereas the response and recovery times without the additional carbon filter over the chip are <500 ms and <2 s, respectively. The tests have shown the reliability of the new design concerning the hotplate stability and massive encapsulation, but the high degradation rate of the catalyst coupled with its modest chemical power limits the use of the sensor only in pulsed mode of operation. The optimized pulsed mode reduces the average power consumption below 2 mW.
Highlights
Combustible gases are among the most serious sources of man-made disasters in the world nowadays, which may result in severe human losses and damage in the built environment
Optical sensors detect variation in light absorption at certain wavelengths specific for each flammable gas [1,2]; the operation principle of semiconductor sensors is based on the change in conductivity of a semiconductor layer when the gas is adsorbed [3,4,5]; the electrochemical flammable gas sensor measures the current based on the electrochemical reaction on the working electrode inside the solid or liquid electrolytic cell [6,7]; the thermocatalytic sensor principle is based on a change of the microhotplate temperature when the gas burns on its surface [8,9]
The developed thermocatalytic device has a pair of full membranes, which are produced by Silicon MEMS technology with two built-in embedded meander-like filaments
Summary
Combustible gases are among the most serious sources of man-made disasters in the world nowadays, which may result in severe human losses and damage in the built environment. We have to keep on monitoring leaks of combustible gases to prevent the accidents associated with gas explosion. Four gas sensing technologies are commonly used for detecting combustible gases in the environment near the lower explosive limit (LEL): optical, semiconductor, electrochemical, and thermocatalytic. Optical sensors detect variation in light absorption at certain wavelengths specific for each flammable gas (except for H2 , which has no absorption band) [1,2]; the operation principle of semiconductor sensors is based on the change in conductivity of a semiconductor layer when the gas is adsorbed [3,4,5]; the electrochemical flammable gas sensor measures the current based on the electrochemical reaction on the working electrode inside the solid or liquid electrolytic cell (mainly used for H2 ) [6,7]; the thermocatalytic sensor principle is based on a change of the microhotplate temperature when the gas burns on its surface [8,9].
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