Q

What is a gas sensor gas sensor symbol?

A

A component (or component) that can sense a certain gas and convert the gas concentration into an electrical signal is called a gas sensor. There are many types of gas sensors, and there is currently no special symbol. When drawing circuit diagrams, you can design symbols yourself and cooperate with text descriptions.

Q

What are the commonly used gas sensors?

A

1. Semiconductor gas sensor; 2. Electrochemical gas sensor, high precision, good selectivity, expensive, generally detects toxic gases such as carbon monoxide, H2S, SO2, etc.; 3. Catalytic combustion gas detector, detects flammable gases, There is no selectivity, and it responds to flammable gases such as gas, propane, etc., because the material uses a catalyst, and attention should be paid to poisoning during use; 4. Infrared gas sensor; 5. PID sensor, which is a light particle type, and the price is good Expensive, non-selective, PPM-level detection; 6. Laser gas sensor, which is rarely used in China; 7. Thermal conductivity type gas sensor, which measures high-concentration gas.

Q

How to choose MEMS smoke gas sensor?

A

According to personal experience, choosing the right company is choosing the right product. I recommend Seiya smoke sensor, which is more authoritative in chip technology and MEMS packaging. The product is small in size, low in power consumption, and high in sensitivity, and has cooperated with brands such as Huawei, Gree, Haier, and Midea, which is very good. Other brands may not know much about them, so we can still trust these domestic electrical appliance brands, right?

Q

What problems are easily overlooked in the use of combustible gas alarms？

A

1. Using a combustible gas alarm or a portable combustible gas detector in an atmosphere with insufficient oxygen may cause the reading of the combustible gas to be lower than the actual concentration. On the contrary, using a combustible gas alarm or a combustible gas detector in an environment with sufficient oxygen Detected combustible gas readings may be higher than actual concentrations. 2. When the reported concentration of combustible gas causes the instrument to display "over range", it is necessary to re-calibrate the combustible gas sensor. For example, in the process of using the combustible gas alarm, the measuring range of the instrument is 0-100% LEL, but when the actual concentration is higher than 100%, it will cause the phenomenon of over-range, at this time, it is necessary to re-calibrate the gas sensor. 3. Water vapor or other known impurities of silicone compounds may affect the normal operation of the combustible gas sensor, causing its reading to be lower than the actual gas concentration. If the instrument has been used in the water vapor environment of silicone compounds, in order to ensure the accuracy of the measurement, please re-calibrate the instrument before the next use.

Q

What matters should be paid attention to when using the body detection alarm？

A

Gas detection alarms are widely used in large-scale industrial production processes, especially in the fields of electric power, electronics, petroleum, chemical industry, coal, pipe gallery and other fields. They can monitor the gas status in real time to ensure safe production and environmental protection. Infected. But in the process of using the gas detection alarm, we must be careful. Today, the editor will take stock of the precautions in the use of its gas detection alarm for us.

Q

The difference between electrochemical sensors and semiconductor sensors？

A

Electrochemical sensors are prepared based on the principle of electrochemical oxidation and reduction of gases, which is almost the same as our batteries. For example, we detect carbon monoxide, CO is oxidized to carbon dioxide at the anode of the electrolytic cell, and the electrolysis current is related to the concentration of CO. Semiconductor sensors are based on metal oxide semiconductor materials. In the air, when the redox state of the air changes, the conductivity of the semiconductor material will change accordingly. For example: when a certain concentration of alcohol vapor is diffused in the air , the conductivity of the tin dioxide semiconductor material will increase and the resistance will decrease; and the magnitude of this change is directly related to the concentration of the gas. This is a semiconductor gas sensor! The electronic nose under our family range hood uses this sensor.

Q

Employment Prospects for Semiconductor Sensor Professionals？

A

Very well, with the development of science and technology, sensors will be more and more widely used in the future society, and the demand is very large, so the development prospect of the sensor field must be very good, so what about the employment situation? Since sensors are a multidisciplinary field involving materials, chip technology, packaging, circuits, software, machinery, etc., the employment directions of sensors are also divided into many types, which cannot be generalized. Engaging in different directions, the treatment you get and your future career development also have a great impact.

Q

Why do semiconductor sensors need heating?

A

The semiconductor sensor is an impedance device made of a metal oxide film, and its resistance varies with the gas content. Gas molecules undergo a reduction reaction on the surface of the film to cause a change in the conductivity of the sensor. An oxidation reaction must take place in order to eliminate the gas molecules to the initial state. The heater in the sensor can accelerate the oxidation process, which is why some low-end sensors are always unstable. The reason is that there is no heating or the heating voltage is too low, resulting in insufficient reaction at too low temperature.

Q

What is the working principle of semiconductor gas sensor?

A

Under certain temperature conditions, when the measured gas reaches the surface of the semiconductor sensitive material, it will chemically react with the oxygen adsorbed on the surface, and cause the resistance of the semiconductor sensitive material to change. The resistance change rate is exponentially related to the measured gas concentration. By measuring The gas concentration can be measured by the change in resistance. A single semiconductor gas sensor can achieve limited recognition of gases in a known environment by means of selective catalysis, physical or chemical separation. Large-scale semiconductor gas sensor arrays can realize accurate identification of gas species in unknown environments.