Patent ID: 7358489
Filing Date: 2008-04-15
Classification: G01N

Abstract:
1. In a single beam NDIR gas sensor for detecting the concentration of a gas species in a sample chamber with a differential infrared source element that can produce radiation having a first spectrum when its temperature is at a first high temperature and a second spectrum when its temperature is at a second lower temperature, a detector for generating a detector output and a dual pass band filter located between the source element and the detector, the improvement of which comprises: a driver for driving the source at either the first or the second temperature; a feed back loop to sense an operation voltage of the source; a differential gain amplifier for creating a high cycle amplified output during a high cycle and a low cycle amplified output during a low cycle; a controller for synchronizing the driver so that the source is driven at the first temperature and a high cycle amplification is applied to the detector output during the high cycle and the source is driven at the second temperature and a low cycle amplification is applied to the detector output during the low cycle; and a signal processor for determining the concentration of the gas species through use of the high cycle amplified output and the low cycle amplified output.