Working principle of electrochemical gas sensor

In a small sensor, an electrode that is wetted by aqueous gel electrolyte (typically sulfuric acid: H2SO4), when the detected gas (such as carbon monoxide: CO, or hydrogen sulfide: H2S) enters the sensor and oxidation or concentration change in the sensor When the working electrode produces a weak current under the action of the catalyst. The current is enlarged through the amplifier connected to the sensor to show the gas concentration of the target area. Be Typical structure of electrochemical sensors Most electrochemical gas sensors are applied to diffusion mode, in which gas samples in the surrounding environment enters the sensor (by gas molecule natural flow) through the small holes front of the sensor. Some devices take the air / gas sample into the sensor through a pump. A polytetrafluoroethylene film is attached to the pore portion to block water or oil into the sensor. The measurement range and sensitivity of the sensor can be adjusted in the design of the intake hole. Biggest intake holes can increase the sensitivity and resolution of the equipment, while small intake holes reduce sensitivity and resolution, but increase the measurement range. The working principle of the oxygen sensor is similar to the working principle of the electrochemical oxygen sensor previously described, but the use of the oxygen sensor is predictable, so the replacement period can also be preset - generally 2 to 3 years. Unlike the toxic gas sensor, the oxygen sensor continues to expose in the target gas for a long time. In the usual oxygen monitoring applications, the sensor working environment has a concentration of 20.9%, which will cause chemical reactions on the lead anode, resulting in a gradual consumption of the anode. Therefore, the ability of the sensor to continuously generate current by reaction with oxygen depends on the content of lead in the electrolyte. The gas detection equipment manufacturer ensures the performance of the sensor by increasing the key mechanism of "temperature compensation". Gas sensitivity (and zero-based line signals) often have changed with temperature, so when the temperature is lifted, the gas sensitivity is non-linear. In the process of R & D gas detection equipment, people use a large amount of time to place the same gas sensor in different temperatures and different concentration gases (temperature between -30 ° C ~ +50 ° C). The collected data is processed after processing a temperature compensation algorithm used for gas detectors to ensure that sensor readings are consistent throughout the operating range. Read more

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