Gas sensors include various types. For flammable gas sensors, for example, contact combustion type, semiconductor type, heat conduction type, infrared absorption, etc. have been known as described in JIS M 7626 “Stational Type Combustible Gas Detection Alarm”. Further, as a system of using thin films or thick films, an FET system (system of depositing gas sensing membrane on a gate electrode of FET and reading the change of the gate potential caused by a target gas) by using the FET as described in the Journal of Sensors and Actuators, Vol. B1, pp 15 to 20, or a thermoelectric system (system of reading the temperature rise of a thermoelectric conversion membrane by a target gas as a voltage) as described in Japanese Journal of Applied Physics, Vol. 40, pp L1232 to 1234 has been proposed.
While the examples described above concern the single sensor elements per se, a method of detecting a hydrogen gas in a wide range of concentration by using plural sensors of different output linear regions relative to the concentrations (JP-A No. 2002-357576) has been laid-open as an example of using plural sensors.
It has been expected that detection systems of measuring not only the gas concentration at specified positions but also measuring the distribution of the gas concentration over entire facilities and consequence monitoring f or the leakage diffusion and determining the leaked position will be popularized in the feature. Since hydrogen filling stations for supplying hydrogen gas to fuel cell vehicles are built in city areas and required high safety, they are typical example of facilities requiring such detection systems.
A technique of connecting plural gas sensors by way of wireless communication and monitoring the concentration distribution of a gas has been described, for example, in the 10th International Meeting on Chemical Sensors, Technical Digest, pp 94 to 95. This example proposes to hybridize several kinds of sensors such as electrochemical sensors or optical ionization sensors and construct a VOC monitoring system for odors in waste water treating plants, dust disposing plants, livestock barns, clean rooms, etc.
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-357576
[Non-Patent Document 1]
Journal of Sensors and Actuators, vol. B1, pp 15 to 20
[Non-Patent Document 2]
Japanese Journal of Applied Physics, vol. 40, pp L1232 to L1234.
[Non-Patent Document 3]
The 10th International Meeting on Chemical Sensors, Technical Digest, PP 94 to 95