TGS2600 is a semiconductor air sensor produced by FIGARO Corporation of Japan. It can sensitively sense the odor of low-concentration impurities in the air, and has the characteristics of low cost, small volume, long life, selectivity and stability. The TGS2600 can be used to align the internal structure and working principle of the TGS2600 air sensor, and introduces an air quality monitoring circuit designed with the TGS2600 and specific air quality monitoring results.

0. Preface

In the atmosphere, air quality monitoring has received more and more attention from people. Many enterprises and research institutions at home and abroad have made great progress in the field of gas sensor research and development. At present, gas sensors are becoming integrated, intelligent, and the direction of multi-parameter detection is developing rapidly. . The series of semiconductor gas sensors developed and manufactured by FIGARO Corporation of Japan represents the latest level in the field of existing gas sensors, and has created favorable conditions for research and development of air quality monitoring systems, providing a simple and practical approach.

1. semiconductor gas sensor and its characteristics

The semiconductor gas sensor detects a gas by utilizing a change in physical properties such as electrical conductivity when a gas to be tested is in contact with a surface of a semiconductor (mainly a metal oxide). The semiconductor gas sensor is heated to a steady state. When the gas contacts the surface of the device, the adsorbed molecules first diffuse freely on the surface (physical adsorption), lose their kinetic energy, some of the molecules evaporate, and the residual molecules are thermally decomposed. Fixed at the adsorption site (chemical adsorption). At this time, if the work function of the device is smaller than the electron affinity of the adsorbed molecule, the adsorbed molecule resetting device takes electrons and becomes negative ion adsorption. The most typical gas with negative ion adsorption potential is O2, called an oxidizing gas or an electron-accepting gas. If the work function of the device has such a positive ion absorption adsorption, there are H2, CO, hydrocarbons and alcohols, etc., which are called reduced gases or electrons. Supply gas.

There are many sensitive elements currently available for gas detection, such as SnO2, ZnO, Fe2O3 and gas sensors. Their common feature is the ability to detect many different gases, but the selectivity to gases is poor. This non-single selectivity is determined by its sensitive mechanism. Although it can be improved by adding appropriate amounts of precious metals such as Pt, Pd, etc., it still allows certain other gases to have certain sensitivity.

2. semiconductor air quality sensor TGS2600

2.1 TGS2600 composition and working principle

The air sensor is one of the semiconductor gas sensors, which is simple in structure and consists of a sensor substrate, a gas sensor and a sensor module. The gas sensor consists of a metal oxide sensitive chip with a metal aluminum substrate and a complete heating. When detecting a gas, the conversion rate of the sensor depends on the change in gas concentration in the air. In the absence of the target gas. In the state, O2 in a large amount of attached air captures electrons and exhibits a high-resistance state; conversely, if a target gas exists, a combustion reaction is generated with oxygen, and the amount of free electrons increases, and the resistance value Then lower. A measurement circuit converts the change in rate into an output signal corresponding to a change in gas concentration.

TGS2600 is a new type of semiconductor gas sensor developed and manufactured by FIGARO Corporation of Japan. It can sensitively sense the odor of low-concentration pollutants in the air, such as low-concentration cigarette volume and other odors in the air, and has high H2, CO, etc. The concentration of TGS2600 has the characteristics of low cost, small volume, long life, good selectivity and stability. It can be widely used in air quality monitoring and automatic ventilation and ventilation system. The device is suitable for continuous operation in the next continuous power supply. By using a miniaturized chip, the sensor of the TGS2602 sensor requires only 42mA and is placed in a standard TO-5 package. .

2.2 TGS2600 sensor basic measurement circuit

The basic measurement circuit of the sensor is shown in Figure 1. This sensor requires two voltage inputs: sensor voltage VH and circuit voltage VC. The sensor voltage VH is applied to the integrated heater to maintain the sensor at a particular optimum sensing temperature. The sensor has polarity so the circuit voltage VC must be DC. A common power supply can be used to simultaneously provide the electrical requirements of the VH and VC sensors. Reasonably select the load resistor RL to optimize the alarm threshold voltage and reduce the size to 15mw. When the target gas is present, the sensor is placed at the maximum when RS is similar to RL.

2.3 TGS2600 sensor sensitivity characteristics

2.3.1 Typical sensitivity characteristic curve

Typical sensitivity characteristics are shown in Figure 2. All data is collected under standard test conditions, and the Y-axis represents sensor sensitivity, ie, resistance ratio RS / R0. Where RS is the resistance of the sensor at different gas concentrations; R0 is the resistance of the sensor in fresh air.

2.3.2 TGS2600 sensor typical temperature, humidity dependent characteristic curve

Similarly, the Y-axis represents the sensor sensitivity (resistance ratio) RS / R0, where RS is the resistance of the sensor in fresh air under different temperature and humidity conditions; R0 is the sensor in fresh air at 20 ° C and 65% relative humidity Resistance.

Typical application of TGS2600 sensor

3.1 experimental circuit

There are two options for analyzing and processing the sensor output signal: one is to use the dedicated module developed by FIGARO, the air quality control board AM-1, which has a dedicated replacement (FIC93619A) that contains the sensor signal. Special software, with temperature and humidity compensation, provides a new and simple means of air quality testing; the second is to replace other models and program the signal processing.

AM-1 is a pollution monitor that allows users to understand and notice the high sensitivity and excellent performance of the TGS2600 sensor in air quality monitoring in the shortest time. It can cause abnormalities in indoor air to be similar to human perception. AM-1 is divided into four. The AM-1 accurately senses the changes in the burning of a cigarette in a 50m3 room. Its good sensitivity is obtained by changes in resistance. The AM-1 is rated in four levels to assess the degree of contamination in the room, which can be indicated by five different colored LEDs. The sensor signal is corrected after processing to determine the air quality into four levels. As shown in Table 1. At the same time, these several output signals can control the action of the air freshener, let it reset, weak operation, medium operation or strong operation, so as to achieve the purpose of regulating and fresh air. This series of operations is very consistent with people's ideas. Designed with a sensitivity switch on the AM-1, there are “H” and “L” options to choose from, depending on the needs and application.

3.2 Experimental results

The AM-1 was fixed in a test box with a space of 1 m3, with a camera and venting holes in the box, and a glass viewing window around the box. After power-on, warm up for 3 minutes, when the green light flashes. If the air quality is good, the green light is on. Using the experimental circuit of Figure 4, the output signal of the sensor is sent to the NR2000 collector, and then sent to the computer through the USB interface. Burning paper, cloth, plastic, nylon and cigarettes in the box, the test data shows that TGS2600 has high sensitivity and good resolution, which reflects the smoke generated in different stages before combustion, burning and burning. And the smell of the situation.

4. Conclusion

It can be seen from the above experiments that the TGS2600 air quality sensor can well sense the odor of impurities in the air and monitor the change of air quality very sensitively. Compared with other air sensors, TGS2600 has great advantages in sensitivity and stability, and has the characteristics of low cost, small size, long life, low price and good stability. The TGS2600 provides a convenient and reliable method for air quality monitoring and ventilation and ventilation equipment. Taking advantage of the development of the economy and the improvement of people's living standards, people's growing concern about environmental protection issues, especially the monitoring of indoor air quality, is also of increasing concern. Therefore, the development and comprehensive application of air sensors is a matter of urgency. The thesis will surely become a field of applied research that is gradually gaining attention.