Electro Optical Components demos NDIR gas detector

At Sensors Expo 2016, Electro Optical Components Inc. demonstrated a gas sensing evaluation kit using NDIR (nondispersive infrared) sensors. It is called nondispersive because the wavelength that passes through the sampling chamber is not pre-filtered. Instead a narrow bandpass (NBP) filter is used before the detector.

The NDIR sensor is a broadband IR detector using one of the following technologies:
• Thermopile detector or sensor
• Pyroelectric detector or sensor
• Lead Selenide (PbSe) detector or sensor

The NBP filter turns the broadband detector into a very specific narrowband detector that looks at a specific IR band that the target gas absorbs.

The NDIR system needs a broadband IR source. This source can be steady state for thermopiles, but needs to be pulsed for pyroelectric and lead selenide detectors.

The target gas will absorb more IR energy as the gas concentration increases. This means that as the gas concentration increases, the signal from the detector will decrease. Concentrations from % down to ppm can be measured using NDIR. The detectors can be made with multiple channels with different NBP IR filters for monitoring more than one gas.

You can improve the sensitivity of the NDIR gas sensor system by:
• Increasing the gas tube length and reflectivity, optimizing the optical pat

• Using a detector with more sensitivity

• Improving the IR source performance (modulation depth).

Check out Electronic Products’  complete new product coverage of Sensors Expo 2016