Temperature Compensation Algorithm of Nondispersive Infrared (NDIR) Gas Sensor

Abstract - This paper describes the temperature compensation algorithm using thermopile detector for nondispersive infrared methane gas sensor. From the output voltage of thermistor that is attached onto the infrared detector, the ambient temperature was extracted. The effects of temperatures on the properties of sensor module (the characteristics of narrow bandpass filter, optical cavity and infrared lamp, and gas absorption coefficient times optical path length) have been introduced in order to implement the temperature compensation algorithm. Even though the measurement error of developed sensor module was in the range of ± 1,500 ppm, after programming the temperature compensation algorithm, the developed sensor module shows a high accuracy less than +180 ppm error within 20 ℃ temperature variation. Key words : NDIR (Non-Dispersive Infrared), CH4 gas sensor module, thermistor output voltage, narrow bandpass filter, temperature compensation algorithm. † I. 서 론 대기 중 가스 분석법으로 적외선 분광법이 선택성과 내구성이 우수한 것으로 알려져 있는데, 이들에는 퓨리에 변환 적외선 분광기 (fourier transform infra-red spectroscopy), 적외선 가스분석기(infrared gas an-