How does an NDIR CO2 Sensor Work?

NDIR CO2 Sensor

NDIR is an industry term for “nondispersive infrared”, and is the most common type of sensor used to measure carbon dioxide, or CO2.

The CO2 sensor works by directing light waves from an infrared lamp through a tube filled with air samples. This air moves toward an optical filter in front of an IR light detector. The IR light detector measures the amount of IR light that passes through the optical filter.

The band of IR radiation also produced by the lamp is very close to the 4.26-micron absorption band of CO2. Because the IR spectrum of CO2 is unique, matching the light source wavelength serves as a signature or “fingerprint” to identify the CO2 molecule. As the IR light passes through the length of the tube, the CO2 gas molecules absorb the specific band of IR light while letting other wavelengths of light pass through. At the detector end, the remaining light hits an optical filter that absorbs every wavelength of light except the wavelength absorbed by CO2 molecules in the air sample tube.

Finally, an IR detector reads the remaining amount of light that was not absorbed by the CO2 molecules or the optical filter.

How is the CO2 level calculated?

The difference between the amount of light radiated by the IR lamp and the amount of IR light received by the detector is measured. Since the difference is the result of the light being absorbed by the CO2 molecules in the air inside the tube, it is directly proportional to the number of CO2 molecules in the air sample tube.

All measurements start out as analog micro-voltages. While some sensors output this as an analog voltage or 4–20mA signal, some also include an analog to digital converter on the sensor PCB that converts the voltages into serial or RS-485 output. Serial output is especially useful for using NDIR CO2 sensors with Arduino or Raspberry Pi microcontrollers.

Modern NDIR CO2 sensors advantage

1. The stability of THE NDIR CO2 sensor lies in the light source. Our sensor module uses imported infrared light source to improve the stability and service life of the product.

2. The sensor module is gold-plated. In the original high performance on the basis of the product to add security.

3. We can meet customer needs, can customize the voltage output range and corresponding range.

4. The data will be automatically calibrated when the user is using the module.

Article source: https://article-realm.com/article/Communications/VOIP/27833-How-does-an-NDIR-CO2-Sensor-Work.html