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NDIR CO2 sensor introduction and selection

NDIR CO2 sensor introduction and selection
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NDIR CO2 sensor introduction and selection - 1

NDIR Carbon Dioxide (CO2) SensorIntroduction and Selection Cubic Nowadays, NDIR CO2 sensor based on non-dispersive infrared technology is extensively used in various fields like ventilation system, indoor air quality (IAQ) monitor, green house, etc to measure CO2 concentration, and help HVAC system to keep controlling ventilation rates and save energy consumption. It has advantages of high accuracy, high stability, long lifespan and good selectivity, wide range, etc. So NDIR CO2 sensor is the best choice to ensure the stable performance of the CO2 monitoring. "It requires that CO2 sensors have an accuracy of within plus or minus 75 ppm at 600 and 1,000 ppm levels, and require calibration no more frequently than once every 5 years ”, According to 2016 Building and Appliance Efficiency Regulations. In this article, it will introduce the type of NDIR CO2 sensors and main specifications from 7 aspects for CO2 sensors selection. Types of NDIR CO2 sensors Gas with asymmetric molecular structure has strong absorption of infrared. So NDIR gas sensor only can measure gas with asymmetric molecular structure such as SO2, NO, CO2, CO, CH4, but not to measure O2, H2, N2 with symmetrical molecular structure. Generally, there are three types of NDIR CO2 sensors: single beam single wavelength sensor, dual beam dual wavelength sensor and single beam dual wavelength sensor. Basically, the key components of the sensor are an infrared source, gas chamber and an infrared detector. When light wave corresponded to certain gas with absorption spectrum passes through measured gas, the intensity of light wave will be significantly weakened. The intensity attenuation is related to concentration of measured gas. Single beam NDIR CO2 sensor It is single beam single wavelength sensor integrated with one sensitive component and one narrowband filter lenses. There are many causes of drift problem, such as long time transportation or laid-up, temperature and humidity change, transformation of casing. Thanks to the automatic background calibration function, the sensor could calibrate itself. The sensor will take the lowest CO2 reading as the zero point (400 ppm) within several days. In ventilated environment, the lowest CO2 concentration is close to 400 ppm. One of the most important environment for automatic background calibration is fresh air. In this C. Optical bandpass filter D. Signal channel detector case, single beam CO2 sensor is suggested to be used in indoor air quality monitoring, ventilation system , air conditioner with purifier function , where there is fresh air. Dual beam NDIR CO2 sensor It is mainly reference to single beam dual wavelength sensor. It is with one beam for detecting, another beam for reference. The advantages are good stability, anti-interference, higher accuracy, etc. It is widely used in not ventilated environment such as ventilation system, agricultural greenhouse facilities, agricultural IoT, automotive , etc. C. Optical bandpass filter E. Dual channel detector Wuhan Cubic can provide these two sensor types based on core NDIR gas technology for indoor air quality monitoring.

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NDIR CO2 sensor introduction and selection - 2

Measurement range Different measurement range should be applied in different places. Generally, the measurement ranges of the sensor in the market are three types: 0-2000 ppm (parts per million), 0-5000 ppm, 0-10000 ppm.Carbon dioxide level monitoring for indoor air quality is commonly in 0-2000 ppm. Because the CO2 level in fresh air between 350-400 ppm, and according to the versions of ASHRAE Standard 62, it recommends that the CO2 levels not exceed 1000 ppm inside buildings. Another point is the resolution consideration when we choose the measurement range. Resolution can be relative...

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NDIR CO2 sensor introduction and selection - 3

Signal output Analog signal output and digital signal output are two ways of NDIR gas sensor’s major signal outputs. Analog output has 4-20mA current and 0-5 VDC output, and digital output always uses TTL electrical level UART_TTL for communication working with modbus communication protocol usually. Analog signal output is widely used in industrial, and easy to integrate. However, the disadvantage is the error. The first error inside sensor is caused by digital to analog conversion and the second error is caused by analog signal collection. So that analog output is not suitable for...

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