Introduction
In the field of environmental monitoring and industrial safety, composite gas detectors are widely used for real-time measurement of various gas concentrations. Among them, electrochemical sensors and infrared sensors are two common technical paths. This paper aims to compare and analyze the working principles, performance characteristics and application scenarios of these two sensors, and provide a reference for technology selection in related fields.
How it works:
The electrochemical sensor generates a current signal based on the redox reaction that occurs on the surface of the electrode, which is directly proportional to the gas concentration, and its basic relationship can be expressed as:
I = n × F × A × D × C / δ
Where I is the output current, n is the number of electron transfers, F is the Faraday constant, A is the electrode area, D is the gas diffusion coefficient, C is the gas concentration, and δ is the thickness of the diffusion layer.
The infrared sensor uses the absorption characteristics of gas molecules to infrared light at a specific wavelength, and calculates the gas concentration by measuring the attenuation of light intensity according to Lambert-Biel's law:
A = ε × l × c
where A is the absorbance, ε is the molar absorbance coefficient, l is the length of the optical path, and c is the gas concentration.
Comparison of performance parameters
| Response time | It is usually faster, ranging from a few seconds to tens of seconds |
| Lower limit of detection | It can reach ppm or even ppb level |
| Selectivity | Rely on electrode materials and filtration technology |
| Lifespan | Affected by electrolyte consumption |
| Environmental impact | Temperature and humidity sensitive |
| Calibration cycle | Relatively frequent |
| Response time | Faster, usually within seconds |
| Lower limit of detection | Usually ppm level |
| Selectivity | Based on the absorption spectrum, there is little cross-interference |
| Lifespan | The optical components have a long life |
| Environmental impact | It is disturbed by dust and water vapor |
| Calibration cycle | Relatively long |
Applicable scenario analysis
Electrochemical sensors excel in detecting electrochemically active gases such as oxygen, carbon monoxide, and hydrogen sulfide, especially in applications where portability and low power consumption are required. It is compact and cost-controllable, but can be interfered with by cross-gases, and its service life is affected by the working environment.
Infrared sensors have good detection capabilities for non-polar gases such as carbon dioxide and methane, and are suitable for stationary monitoring of complex background gases that require long-term stable operation. It is not easy to be poisoned and has good stability, but the initial investment is high, and it is more sensitive to water vapor and dust.
Summary
Electrochemical sensors and infrared sensors have their own characteristics and need to be selected with a comprehensive consideration of the target gas, environmental conditions, budget and maintenance requirements. In practical applications, the two technologies are often integrated into the same device to achieve complementary advantages and improve the reliability and coverage of inspections.
References
1. Review of Gas Sensor Technology, Journal of Sensing Technology, 2020.
2. Principles and Applications of Infrared Gas Detection, Analytical Instruments, 2019.
3. Design Guide for Composite Gas Detectors, Safety and Environmental Engineering, 2021.