Details of Non-dispersive Infrared Sensor

Definition: Non-Dispersive Infrared (NDIR) sensor is an optical sensor composed of infrared light source, optical path, infrared detector, circuit and software algorithm. It is mainly used for the determination of compounds, such as CH₄, CO₂, N₂O, Co, CF₄, NO, SO₂, NH₃, ethanol and benzene, and contains most organic compounds. It uses a broad-spectrum light source as the light source of the infrared sensor. The light passes through the measured gas in the optical path, through the narrow-band filter, and reaches the infrared detector. By measuring the intensity of the infrared light entering the infrared sensor, the concentration of the measured gas can be judged. NDIR can measure the gas that common sensors used for temperature measurement(such as catalytic combustion and electrochemical sensors) can not do, like the measurement of CO₂. The most common gases to be measured in NDIR are CH₄, CO and CO₂.

1. What is the advantage of NDIR sensor over catalytic combustion in measuring organic gas?

Although the catalytic combustion sensor can measure combustible gas, it will be poisoned when encountering gas containing fluorine, chlorine, bromine, sulfur, and organic silicon, and its sensitivity will be permanently reduced. But under the same conditions, the NDIR sensor will not be affected, because the light source and the detector are protected by glass or filter, and they are not in contact with gas.

2. What is the biggest advantage of NDIR sensor?

Non-dispersive infrared sensor has one of the biggest advantages: excellent long-term stability and low maintenance cost, which is also the main reason for the rapid growth of NDIR sensor sales. At present, it is estimated that about 3% to 5% of industrial gas meters use NDIR sensors, with an annual growth rate of about 10%.

3. Advantages of NDIR sensors

Anti poisoning, oxygen free, excellent long-term stability, wide temperature range, measuring concentration to 100% Vol.

4. Two technical routes of NDIR sensors:

(1) It is applied in analytical instruments, which is featured by high resolution, long wavelength and multiple gases.

(2) It is applied in indoor air quality IAQ testing and power SF6 leakage testing to test CO₂ and hydrocarbon HC gases. These applications are featured by small size and low cost and their global sales volume is about several million.