How to test the lifespan of electrochemical gas sensors?
With the rapid development of sensor technology, gas sensors are increasingly being used in various application scenarios and have become an important gas detection device. For any sensor, there is a certain time range for its service life. So, how to detect the service life of a gas sensor? What are the detection methods?
We all know that it is impossible to use one type of sensor to detect all gases and meet all requirements. Depending on the gas and environment, different gas sensors are used. Gas sensors can be roughly divided into sensors that detect the explosion concentration of combustible gases, and sensors that detect the concentration of toxic gases.
We all know that it is impossible to use one type of sensor to detect all gases and meet all requirements. Depending on the gas and environment, different gas sensors are used. Gas sensors can be roughly divided into sensors that detect the explosion concentration of combustible gases, and sensors that detect the concentration of toxic gases.
The sensors used to detect the concentration of combustible gases are mostly catalytic combustion sensors, and their service life is 3-5 years under ideal conditions. The service life of gas detectors (including fixed gas alarms and portable gas alarms) is closely related to the concentration it is exposed to. For example, if a sensor of an ammonia detector is continuously exposed to 2ppm of ammonia, its service life is about one year (or called 2ppm-year service life), while if it is exposed to 4ppm of ammonia concentration, it only has a life of six months.
If gases are adsorbed, the gas concentration will also decrease. For example, SO2, NH3, NO2, HCL, and other gases have strong adsorption properties. Therefore, it is recommended to use a polytetrafluoroethylene tubing gas path to reduce gas adsorption when monitoring these gases. Before starting the test, the air should be vented for 5 minutes to discharge the air in the gas path.
The sensors used to measure the concentration of toxic gases are mostly electrochemical gas sensors, which are gas sensors based on the principle of electrochemistry. The main factor that affects their service life is the electrolyte. In ideal conditions, the electrolyte for most sensors is consumed and cannot function properly after 2-3 years, so the service life of electrochemical gas sensors is 2-3 years. Most gas sensors are sensitive to environmental temperature and humidity. If the humidity changes significantly (for example, entering a humid outdoor air environment from a dry environment with air conditioning), water vapor in the air will displace the gas, which may cause a significant drop in gas readings.
The higher the environmental temperature in a short period of time, the more intense the chemical reaction and the more likely it is to affect the accuracy of the gas sensor and the sensor signal output in the detection process. If the sensor is in a high-temperature and low-humidity environment for a long time, it is easy to evaporate and dry the electrolyte, which will limit electronic transfer, increase internal resistance, slow down response speed, reduce sensitivity, and affect the sensor’s service life. In order to reduce the impact of environmental temperature and humidity on gas sensors, temperature and humidity compensation is the most direct and effective solution.
Gas sensors have wide applications in modern society. What are their specific functions?
Gas sensors are particularly suitable for gas detection. For example, an oxygen sensor can detect the oxygen content in the air. When oxygen gas diffuses through the micropores on the casing onto the surface of the working electrode via the gas-permeable membrane, it reacts with the working electrode under catalysis. The H+ ions and electrons generated from the oxidation reaction on the working electrode are transferred to the counter electrode, which is kept at a certain distance from the working electrode, through the electrolyte and react with oxygen in the water. When the gas sensor generates the output current, its magnitude is proportional to the gas concentration. By measuring the output current of the sensor through the electrode lead wire and the external circuit, the oxygen concentration can be detected, and the sensor has a wide linear measurement range. Thus, by connecting the signal acquisition circuit and the corresponding conversion and output circuit to the gas sensor, the detection and monitoring of oxygen gas can be achieved. It is widely used in mining, monitoring instruments, environmental pollution emission, and other scenarios that require oxygen gas detection.