News
Industry NewsWhat is NDIR sensor?
NDIR (Non-Dispersive Infrared) is a gas detection technology based on the principle of infrared absorption. It is widely used in high-precision measurement of gases such as CO₂, methane (CH₄), and refrigerants (such as R134a).
1.Working principle of NDIR sensor
NDIR sensors determine concentration by detecting the absorption of specific infrared wavelengths by the target gas. The core process is as follows:
Infrared light source: emits broad-spectrum infrared light (usually in the wavelength range of 2–14 μm).
Gas absorption: The target gas (such as CO₂, which has a strong absorption peak at 4.26 μm) absorbs light of a specific wavelength.
Detector detection:
Reference detector: measures the wavelength that is not absorbed (as a benchmark).
Main detector: measures the attenuation of light intensity after being absorbed by the gas.
Concentration calculation: According to the Lambert-Beer Law, the gas concentration is inverted by the degree of light intensity attenuation.
2. Core components of NDIR sensor
| Components | Material/Type | Function |
| Infrared light source | Miniature tungsten lamp, LED or laser IR source | Emitting stable infrared light |
| Air chamber | Aluminum alloy/gold-plated inner wall (anti-corrosion) | Gas flows through the path, and the optical path length affects the sensitivity. |
| Filter | Narrow-band interference filter (such as 4.26μm) | Only the wavelength absorbed by the target gas is allowed to pass. |
| Detector | Thermopile or photodiode | The optical signal is converted into an electrical signal. |
| Reference channel | Wavelength without gas absorption (such as 3.9μm) | Environmental interference is eliminated(Temperature, dust, etc.) |
3. Features of NDIR Sensors
✅ High accuracy: up to ±50 ppm (CO₂) or ±2% FS (full scale).
✅ Long life: no chemical consumption, life is usually 5–10 years.
✅ Anti-interference: only responds to the target gas, not affected by other gases.
❌ Limitations:
①Unable to detect gases without infrared absorption (such as H₂, O₂).
②Higher cost than electrochemical or semiconductor sensors.
4. Typical application scenarios
Indoor air quality (IAQ): CO₂ monitoring (office, school, smart home).
Industrial safety: methane (CH₄), sulfur hexafluoride (SF₆) leak detection.
Automotive electronics: vehicle air conditioning refrigerant (R134a) monitoring.
Agriculture: greenhouse CO₂ concentration control.
5. NDIR vs. other gas sensors
| Type | NDIR | Electrochemistry | semiconductor(MOS) |
| Principle | Infrared absorption | Chemical reactions | Surface resistance change |
| Accuracy | High (±2% FS) | Medium (±5% FS) | Low (greatly affected by temperature and humidity) |
| Life | 5-10 years | 2-3 years | 1-2 years |
| Cost | high | medium | low |
| Applicable gas | CO₂, CH₄, refrigerants, etc. | CO, H₂S, O₂, etc. | VOC, alcohol, etc. |
6. How to choose an NDIR sensor?
Range: For example, CO₂ usually uses 0–5000 ppm (indoor) or 0–100% (industrial).
Power consumption: Low power design (such as TNDIR technology) is suitable for battery-powered devices.
Output signal: Digital output (UART/I2C) or analog output (0–5V).
Summary
NDIR sensors achieve highly selective and long-life gas detection through the principle of infrared absorption, and are the gold standard for CO₂ and hydrocarbon monitoring. Although the cost is relatively high, its reliability and accuracy make it irreplaceable in high-end applications!
If anyone who need to know more about NDIR sensor technology, pls don't hesitated to contact us:
ShanXi TengXing Sensor TechnologyCo.,Ltd
website: www.tensensor.com
email: [email protected]
Message
E-mail
Whatsapp
