The CGS500-IR sensor is a NDIR (non dispersive infrared) sensor designed to replace thermocatalytic gas sensors for monitoring hydrocarbon gases in the range 0-100% LEL. The CGS500-IR is available as a sensor only or fitted in an EEx e certified junction box.
The CGS500-IR uses advanced miniaturised NDIR technology combined with surface-mount microprocessor and firmware technology. A pulsed infrared source emits a broad spectrum infrared beam within an optical cavity. The system measures the adsorption of infrared energy as it passes through a gas sample. Different gases have clearly defined absorption characteristics, their concentration can be determined by their absorption of infrared radiation at the wavelength determined by filter lambda 1 in the diagram.
To compensate for interfering factors filter lambda 2 isolates another wavelength which is used to measure the total transmission through the optical cavity and is not affected by the gas being monitored. By comparing the infrared energy reaching each of the two detectors, the concentration of the gas sample can be determined. The signal processor compares and linearises these two signals. A thermistor monitors the sensor temperature and the signal processor factors in variations caused by temperature changes.