The working principle and main characteristics of gas sensor

Sensor technology is an important technical foundation of new technology revolution and information society, and an important link to realize automatic test control, which has been deeply involved in various fields of people's life. With the increasing popularity and application of microcomputer and microelectronic technology, the performance, quantity and use of sensors have been put forward new demands, and more attention has been paid to the development of new sensors.

Gas sensor is a device that can convert some information of gas, including concentration and type, into acoustic, electrical, optical or digital information that can be used by workers, instruments and computers, etc. It is usually installed in the monitoring system inside the detection head of the monitoring system for collecting air data on site. The gas signal is converted into electrical signal by the gas sensor, and then transmitted to the MCU for data processing through serial communication. Gas sensor is the core of gas monitoring system, which plays a decisive role in gas detection system.

From the working principle, characteristic analysis to measurement technology, from the materials used to manufacturing process, from the detection object to the application field, can form an independent classification standard, derived a complex classification system, especially in the classification standard has not been unified, it is very difficult to carry out strict systematic classification. Next, learn about the main characteristics of gas sensors:

1. Stability

Stability refers to the stability of the basic response of the sensor during the whole working time, which depends on zero drift and interval drift. Zero drift refers to the change of sensor output response during the whole working time when there is no target gas. Interval drift refers to the change of the output response of the sensor continuously placed in the target gas, which is manifested as the decrease of the sensor output signal during the working time. Ideally, a sensor should have a zero shift of less than 10% per year under continuous operating conditions.

2. Sensitivity

Sensitivity is the ratio of the change in the sensor output to the change in the measured input, and depends mainly on the technology used in the sensor construction. Most gas sensors are designed based on biochemistry, electrochemistry, physics and optics. The first consideration is to select a sensitive technique that has sufficient sensitivity to the detection of the percentage of the valve limit or the minimum explosivelimit of the target gas.

3. Selectivity

Selectivity is also known as cross sensitivity. It can be determined by measuring the sensor response generated by a concentration of interfering gas. This response is equivalent to the sensor response produced by a given concentration of the target gas. This characteristic is very important in the application of tracking multiple gases, because cross sensitivity reduces the repeatability and reliability of the measurement, the ideal sensor should have high sensitivity and high selectivity.

4, corrosion resistance

Corrosion resistance refers to the ability of the sensor to be exposed to high volume fraction target gases. In the case of a large amount of gas leakage, the probe should be able to withstand 10~20 times the expected gas volume fraction. Sensor drift and zero correction should be as small as possible under normal operating conditions. The basic characteristics of gas sensor, namely sensitivity, selectivity and stability, are mainly determined by the selection of materials. Selecting appropriate materials and developing new materials can make the sensitive characteristics of gas sensor better.