Method and apparatus for infrared sensing of gas

摘要: A gas sensor (10) is shown having alternately energized infrared radiation sources (14, 16) disposed in a chamber (12) at different distances from an detector (18). Both are filtered the absorbing wavelength of to be monitored with one source located proximate serving as "virtual reference". The differential absorption between two used determine concentration being monitored. In modified (30) seated parabolic recess (34a) base plate (34) focused on angled end wall (32d) dished shaped cover member (32) and reflected over second (32e) into attached directly circuit board (24) mounting sensor. recessed opposed walls also another embodiment which both same distance detector, sensing reference filters, respectively. (50) has concave (32e') vertically aligned (60) additional (18') along semi-reflective, semi-transmitting optical baffle (32k) for use higher level. This shows (32") received (24') no intermediate plate.