[Dry goods sharing] Precautions for the use of electrochemical gas sensors

[Dry goods sharing] Precautions for the use of electrochemical gas sensors
The electrochemical gas sensor works by reacting with the measured gas and generating an electrical signal proportional to the gas concentration. A typical electrochemical gas sensor consists of a sensing electrode (or working electrode) and a counter electrode, separated by a thin electrolytic layer.

The gas diffuses into the working electrode of the sensor through the back of the porous membrane, where the gas is oxidized or reduced, and this electrochemical reaction causes a current to flow through the external circuit. In addition to measurement, it is necessary to amplify and process other signals; the external circuit maintains the voltage passing through the sensor and the voltage of a two-electrode back-reference sensor. A reverse reaction occurs at the reverse electrode. In this way, if the working electrode is oxidized, the opposite electrode is reduced.

As a low-power, high-sensitivity sensor, the electrochemical gas sensor mainly measures oxygen and various toxic gases, and is widely used in limited space scenarios. What should we pay attention to when using electrochemical gas sensors?

Note 1: Soldering cannot be used during installation.

Soldering is a welding method that uses low-melting metal solder to heat and melt, infiltrate and fill the gap between the metal parts. It is widely used in the electronics industry. However, soldering cannot be used when installing the electrochemical gas sensor.

Reason 1: The outer packaging of the electrochemical gas sensor is made of plastic materials, and the temperature is high during soldering, which easily deforms the sensor shell and causes electrolyte leakage.

Reason 2: The heating wire inside the electrochemical gas sensor will form a protective oxide film on the surface in a high temperature environment. The oxide film will age after a period of time, forming a cyclic process of continuous generation and destruction, heating The internal elements of the silk are constantly consumed, and it is very easy to produce broken wires.

Reason 3: The electrolyte inside the electrochemistry is a solvent that can carry out the electrolysis reaction and transfer the ionic charge to the electrode. High temperature will destroy the internal electrolyte, make the electrolyte evaporate, and cause damage to the sensor.

The correct installation method: first solder the pins on the circuit board, and then insert the sensor on the circuit board.

Note 2: Do not tear off the gas permeable film on the gas sensor

The permeable film is the white film above the gas sensor, which is used to cover the upper cover of the sensor or the upper end of the electrode to provide mechanical protection for the sensor, and Filter out some unwanted particles. Gas can enter the inside of the sensor through the breathable membrane. The breathable membrane does not need to be removed during use. If it is removed, this protective effect will be lost.

Correct use method: Keep the white breathable film on the gas sensor and install it on the circuit board.

Note 3: Do not remove the spring on the pin.

When you get the electrochemical gas sensor, you will find that the two pins of the sensor are connected by the spring. You will want to remove the spring. The approach is wrong. The spring connecting the two pins of the electrochemical gas sensor acts as a short circuit. When the electrochemical gas sensor is not in use, charge will accumulate at both ends of the electrode. A short circuit is to release the charge to ensure charge balance and reduce the aging time of the sensor.

Correct use method: When the gas sensor is not in use, the spring needs to be kept, and when it is used, the spring needs to be removed and installed on the circuit board.

Note 4: Do not place the sensor in an oxygen-free environment for a long time.

In an oxygen-free environment, the electrochemical sensor cannot undergo redox reactions and cannot work. If the sensor is placed in an oxygen-free environment for a long time When it is used again, the recovery time will be longer, which will affect the use.

Correct placement method: When storing the electrochemical gas sensor, you need to pay attention to whether there are organic gases and other interfering gases, and whether the ventilation facilities in the environment are good, etc., to ensure that the sensor is in clean air.

Note 5: Sensor storage environment

The white breathable membrane on the sensor is also called hydrophobic membrane. In addition to dustproof and breathable, it also has a certain isolation effect to prevent electrolyte leakage. However, because this film cannot be completely sealed, water vapor can easily enter the sensor. Exposure of the sensor to high humidity conditions for a long time may cause excessive moisture accumulation and leakage, which will also damage the sensor.

Correct use method: Store in accordance with the temperature and humidity range indicated in the manual.

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