Fairley, P.D. and Rutt, H.N.
A novel gas concentration monitor using a solid state modulator
Sensors and Actuators B: Chemical, 75, (3), . (doi:10.1016/S0925-4005(01)00760-2).
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In this paper, we demonstrate the application of a novel solid state modulator in monitoring the concentration of a test gas. A widespread cost-effective method of gas concentration monitoring currently uses a blackbody source and pyroelectric detector combined with a filter to isolate the required infrared spectral region. Presently the intensity on the detector is modulated by either a mechanical chopper or by electrically-pulsing the source. The device described by this work uses a continuously-driven blackbody source with a novel solid state infrared modulator operating in the 8-14 µm band to generate the required change in intensity on the pyroelectric detector, eliminating the need for moving parts. The modulator may be incorporated into the detector’s optical window in a more-compact future device. The modulator operation is outlined, and the results of determining the concentration of SF6 test gas in a dedicated cell are compared for the solid state modulator and a mechanical chopper.
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