Technical principle of the gas detector
Gas detector is a specialized instrument for gas safety concentration detection, its working principle is mainly through the gas sensor acquisition of physical or chemical non-electrical signals into electrical signals, and then through the external circuitry of the above electrical signals rectification, filtering and other processing, and through these processed signals after the control of the corresponding module to achieve the detection of gas. However, the core of the gas detector is built-in sensor components, it is based on the detection of different gases, the distinction between the detection of technical principles are not the same, such as gas detector common technical principles of catalytic combustion, electrochemical, infrared, PID, heat conduction, optical waveguide and other principles, that the partners may know what are the functional characteristics of the differences between them?
1. Catalytic combustion technology principle
Catalytic combustion gas detector technology principle, it is the use of Wheatstone bridge principle, by the detection element and compensation element paired composition of the bridge arm, flameless combustion occurs on the surface of the sensitive body of the detection element when encountering flammable gases, the sensitive body temperature rises, the resistance of the temperature-sensitive material increases, the bridge output voltage becomes larger, the voltage change with the increase in the concentration of the gas and the increase is proportional to the increase in the measurement of the bridge output signal. According to the measurement of the bridge output signal, the size of the change can be determined to detect the concentration of the gas.
2. Semiconductor technology principle
Semiconductor gas detector technology principle, which uses the adsorption of the measured gas to change the conductivity of the semiconductor, through the current changes in the comparison of excitation alarm circuit. Semiconductor type sensors are greatly affected by the environment when measuring, so the output linearity is not stable. Semiconductor sensors are now widely used in the field of measuring the micro-leakage phenomenon of gases due to their very sensitive response.
3. Electrochemical technology principle
Electrochemical gas detector, it is through the sensor and the measured gas reaction and produce and gas concentration proportional to the electrical signal to work. The measured gas first reacts with the sensor through tiny capillary-type openings, then a water-repellent barrier, and finally reaches the electrode surface. A moderate amount of gas is next allowed to react with the sensing electrode to form an adequate electrical signal while preventing electrolyte leakage from the sensor. The gas diffusing through the barrier reacts with the sensing electrode, which can be either oxidizing or reducing.
4. Infrared technology principle
Infrared gas detector technology principle, it is based on Lambert-Beer law, the physical law is when a beam of parallel monochromatic light perpendicular to a uniform non-scattering light-absorbing material, its absorbance and light-absorbing material concentration and the thickness of the absorbing layer is proportional to. Infrared gas detector commonly used infrared wavelength of 2 ~ 12μm, simply put, infrared gas detector principle is to be measured continuously through a certain length and volume of the container, from the container can be transmittance of light in the two end faces of an end face of the side of a beam of infrared light, and then in the other end of the determination of infrared radiation intensity, and finally based on the infrared absorption and the concentration of light-absorbing materials Finally, based on the infrared absorption and the concentration of light-absorbing substances is proportional to the size of the concentration of the measured gas can be known.
5.PID technology principle
Light ionization PID gas detector technology principle, it is through a UV light source, chemical substances in its excitation to produce positive and negative ions can be easily detected by the detector. When molecules absorb high-energy ultraviolet light, ionization occurs, molecules in this excitation produces negative electrons and constitute positive ions. The current generated by these ionized particles is amplified by the detector, and the concentration in ppm level is visible on the surface. These ions pass through the electrodes and quickly recombine together into the original organic molecules. The molecules are not damaged in this process.
6. Heat conduction technology principle
Thermal conductivity gas detector is a new type of combustible gas detection principle, it is mainly through the measurement of the amount of change in the thermal conductivity of the gas mixture to realize the analysis of the concentration of the gas being measured. Usually the difference in thermal conductivity of the thermal conductivity of the gas sensor through the circuit is converted into a change in resistance, the traditional detection method is to send the gas to be measured into the gas chamber, the center of the gas chamber is a heat-sensitive element, such as thermistor, platinum or tungsten filament, heated to a certain temperature, the change in the thermal conductivity of the mixed gases is converted into a change in the resistance of thermal elements, the change in the resistance value of the easier to accurately measure out.
