Respiratory gas analyzer

A detector assembly for use in an infrared spectrophotometer containing an infrared source, a gas sample cell, and at least two narrow band filters positioned in the path of infrared energy, said detector assembly comprising a base, a plurality of thermopile detectors mounted on said base and being responsive to impinging infrared energy to produce an electrical response, an infrared transparent window on the opposite side of said detectors from said base, said detector assembly being unitary and being absent any narrow band filters, said base, detectors, and infrared window being in thermal proximity to each other, said detector assembly further being configured for detachably mounting in said infrared spectrophotometer.

An infrared spectrophtometer comprising, an infrared source for emitting infrared energy, a sample cell for containing gases to be analyzed positioned to be in the path of infrared energy emitted by said source, first, second and third thermopile detectors mounted in thermal proximity to each other and being responsive to impinging infrared energy to produce an electrical response, said first and second detectors being positioned in the path of infrared energy emitted by said source, said third detector being positioned out of the path of infrared energy emitted by said source, a mirror positioned adjacent said third detector for reflecting substantially all infrared radiation emanating from the region of said third detector back onto said third detector, whereby the electrical response of said third detector produces an indication of thermal effects thereon excluding the effect of said infrared source.