Gas detection transmitter situation measuring gas concentration instrument, which is based on a gas sensor, according to different measurement principles, the sensor can be divided into: PID photoionization sensor, infrared sensor, galvanic battery oxygen sensor Constant potential electrolytic gas sensor, catalytic combustion sensor, metal oxide semiconductor sensor, etc.
PID photoionization sensor
PID is composed of ion chamber and ultraviolet light source. There are positive and negative electrodes in the ion chamber, and an electric field can be generated. When the measured gas is irradiated by an ultraviolet lamp, it will be ionized, and then positive and negative ions will be formed. You can generate a current, and then amplify the output signal. This gas sensor has many advantages: safe and reliable, no poisoning and high sensitivity.
Infrared sensor
It works according to the principle of absorption of a specific wavelength by various elements. Its advantages are: very sensitive reaction, good anti-toxicity and corresponding response to many hydrocarbons. The disadvantages are: higher cost and more complicated structure.
Galvani battery oxygen sensor
The relevant structure of the diaphragm galvanic battery-type oxygen sensor is: one side of the plastic container is equipped with a PTFE permeable membrane, its thickness is 10 ~ 30μm, and it has good permeability to oxygen; With the precious metal cathode electrode attached, an anode will be generated in the vacant position of the plastic container or on the inner side of the other side of the plastic container. When potassium hydroxide and oxygen pass through the electrolyte, a redox reaction will occur at the cathode and anode. At this time, the metal of the anode will be ionized, and then electrons can be released. The current is proportional to the amount of oxygen. In the whole reaction, the anode metal will be consumed, so it is necessary to replace the gas sensor within a certain period of time.
Constant potential electrolytic sensor
It is widely used in the field of drug testing. This sensor has advanced technology abroad, but the domestic technology is not mature enough, so it is generally imported products. Its structure is: there is a cylindrical cell made of plastic, the reference electrode, counter electrode and working electrode are installed in it, the electrolyte is filled between the electrodes, and the top is encapsulated by porous tetrafluoro A diaphragm made of ethylene. The gas sensor is connected to the preamplifier, and a voltage is applied between the electrodes to allow the sensor to work normally. The working electrode and the gas in the electrolyte will undergo a reduction or oxidation reaction, while the counter electrode will undergo an oxidation or reduction reaction. At this time, the equilibrium potential of the electrode will change to a certain extent. The amount of change is related to the concentration of the gas. Proportional relationship.
Catalytic combustion sensor
According to the principle of Wheatstone bridge, the combustible gas in the environment reacts with the induction resistance in flameless combustion. The temperature change will cause the change of the induction resistance value, so that the balance of the bridge can be broken, so that it can output a stable current The signal is then amplified, stabilized, and processed by the circuit, and finally a reliable result can be obtained.
Metal oxide semiconductor sensor
It is based on the adsorption of the gas to be measured, so that the conductivity of the semiconductor changes, after comparing the changes in current, you can excite the alarm circuit. When it is working, the environment has a greater influence on its measurement, so the linearity of the output will be unstable. Because the response of this gas sensor is very sensitive, so now it generally measures the phenomenon of gas micro-leakage.
Picture Jasper Necklace,Picture Jasper Beads Necklace,Picture Jasper Beaded Necklace,Picture Jasper Necklace Pendant
JOYA GIFT CO.,LIMITED , http://www.joyagifts.com