Figaro Engineering Inc.

Tomohiro Kawaguchi

Kuniyuki Izawa

Masakazu Sai

Masafumi Toyota

Tatsuya Ishimoto

Kunihiko Maejima

A gas detector uses a MEMS gas sensor having: a substrate provided with a cavity and an insulating film over the cavity; a metal oxide semiconductor and a heater both provided on the insulating film. A drive circuit operates the heater with a predetermined period for a predetermined pulse duration in order to heat the metal oxide semiconductor. The drive circuit halts operation of the heater or elongates the period when a humidity sensor detects that the atmosphere is humid.

Gas detection device and gas detection method

A gas detector includes metal-oxide semiconductor gas sensors and their driving circuit. The gas detector stores the ratio of initial gas sensor resistance in air and that in an atmosphere including Freon gas, for the gas sensors. The gas detector learns sensor resistance in air for a gas sensor in use and detects Freon gas by comparing the sensor resistance of the gas sensor in use with the learned resistance in air divided by the ratio. When the first gas sensor has been used for a predetermined period, both the first gas sensor and a second gas sensor are used for a learning period to continue detection of Freon by the first gas sensor and to learn the resistance in air of the second gas sensor. After completion of the learning period, Freon is detected by the second gas sensor.

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Minoo, Japan

Tomohiro Kawaguchi