Three monitoring principles of ammonia sensor

Three monitoring principles of ammonia sensor

In the chemical industry, ammonia is an important chemical raw material that can be used to make urea, soda ash, ammonium nitrogen fertilizer and nitric acid. At the same time, ammonia is also a kind of gas that easily constitutes a hazard. Because ammonia itself is a flammable and explosive gas, after an ammonia leakage event, it will not only cause harm to the human body, but also cause an explosion. In the chemical industry, the monitoring of ammonia is very important.

Due to the characteristics of ammonia gas, if there is a place where ammonia gas is easy to leak in the work or living field, a portable gas detector should be installed to detect ammonia gas leakage and prevent dangerous accidents caused by excessive leakage.

Currently, there are three major categories of sensors used for industrial ammonia monitoring: optical ammonia sensors, metal oxide sensors, and conductive polymer ammonia sensors.

1. Optical ammonia sensor

The main types of optical sensors are optical interference sensors, ultraviolet absorption sensors, infrared absorption sensors and optical fiber sensors. There are two main optical principles for ammonia detection. One is based on the color of the reagent that reacts with ammonia or triggers the color change of the indicator; the other mechanism is to detect the absorption of light by the gas to complete the sensing to determine the gas concentration.

After the gas to be tested has reacted and colored, it can be analyzed by spectrophotometry. Because the ammonia gas is an alkaline gas at a certain concentration, it can change the color of the pH test paper, so as to analyze whether the atmosphere contains ammonia, but this test needs to ensure that the ammonia concentration is high and the color change of the test paper cannot be sensitively judged, which will produce a large amount error.

The optical sensor can be used to detect the content of ammonia in the environment. It is a gas sensor with high sensitivity and good selectivity. Lasers and spectrographs are the main components of the light absorption ammonia gas detection system. The laser emits light through the air, and the light reaching the detector will have a certain impact on the spectrum of the different gas components in the air and the characteristics of each component, completing the detection of the ammonia content in the gas environment, in terms of sensitivity and selectivity. There are obvious advantages.

Second, metal oxide sensor

The metal oxide gas sensor has become one of the more concerned gas-sensing materials in the formed gas sensor. Research has found that metal oxides such as tin oxide, molybdenum trioxide, and titanium oxide can be used to detect ammonia. The metal oxide sensor has the advantages of sturdiness, durability, low price, simple operation, etc., and it is a very promising gas sensor.

The mechanism of the metal oxide sensor is mainly to adsorb ammonia molecules to the metal oxide sensing layer through chemical adsorption, which causes the conductance of the metal oxide sensor to change, thereby determining the concentration of ammonia gas.

3. Conductive polymer ammonia sensor

The use of conductive polymers can be used to monitor ammonia, such as polypyrrole, polyaniline and polythiophene. Compared with metals and metal oxides, Conductive polymer as a conductive sensor can work at room temperature. The sensing mechanism of conductive polymer for ammonia gas mainly depends on the oxidation-reduction reaction between ammonia gas and conductive polymer. Due to the irreversibility of this reaction, the sensitivity of conductive polymer sensor exposed to ammonia gas for a long time gradually becomes more sensitive. reduce.

The three working mechanisms of the ammonia sensor are optical monitoring, metal oxide monitoring, and conductive polymer monitoring. The ammonia monitoring methods are summarized and summarized. Due to the increasing awareness of environmental protection, the future miniaturization of ammonia gas monitoring sensors is still a trend for gas detection. While ensuring the miniaturization of devices, it is also necessary to ensure that the sensors have low cost, simple operation, high sensitivity and strong selectivity. Features.

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