Principle of electrochemical gas sensor
The two reaction electrodes, the working electrode and the counter electrode, and a reference electrode are placed in a specific electrolyte, and then a sufficient voltage is applied between the reaction electrodes to pass the gas to be tested which is coated with the heavy metal catalyst film. The redox reaction, and then the current generated by the gas electrolysis is measured by the circuit system in the instrument, and then the concentration of the gas is calculated by the microprocessor therein.
Classification of electrochemical gas sensors
The electrochemical gas sensor is a chemical sensor. According to the working principle, it is generally divided into the following types:
(1) when the interface between the electrode and the electrolyte solution is at a certain constant potential, the gas is directly oxidized or reduced, and the current flowing through the external circuit is taken as the output of the sensor;
(2) an ion of a gaseous substance dissolved in the electrolyte solution and ionized is applied to the ion electrode, and the electromotive force thus generated is output as a sensor;
(3) an electrolysis current generated by reacting a gas with an electrolyte solution as a sensor output;
(4) A sensor is fabricated using an organic electrolyte, an organogel electrolyte, a solid electrolyte, a solid polymer electrolyte, or the like without using an electrolyte solution.
Thermal conductivity detection principle:
The thermal conductivity detector is based on the difference between the measured component and the thermal conductivity of the carrier gas. When the composition of the sample passing through the thermal conductivity cell and its concentration change, the temperature of the thermal element changes. , resulting in a change in its resistance value, which can be measured by the Wheatstone bridge
Infrared detection principle:
When a beam of infrared light having a continuous wavelength passes through the substance, the vibration frequency or the rotation frequency of a certain group in the substance molecule is the same as the frequency of the infrared light, the molecule absorbs energy from the original ground state vibration (kinetic energy level) to energy. The higher vibration (rotation) kinetic energy level, the vibration and the rotation level transition of the molecule after absorption of infrared radiation, where the wavelength of light is absorbed by the substance. Therefore, infrared spectroscopy is essentially an analytical method for determining the molecular structure of a substance and identifying a compound based on information such as relative vibration and molecular rotation between atoms within the molecule.
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