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Classification of pressure gauges: Based on their measurement accuracy, pressure gauges can be divided into precision pressure gauges and general-purpose pressure gauges. The measurement accuracy grades of precision pressure gauges are 0.1, 0.16, 0.25, and 0.4 respectively ； The measurement accuracy grades of general pressure gauges are 1.0, 1.6, 2.5, and 4.0 respectively. Gauge pressure instruments are classified into general gauge pressure instruments, absolute pressure instruments, and differential pressure instruments, depending on the reference for the pressure they indicate. Ordinary pressure gauges are based on atmospheric pressure ； The gauge pressure meter is based on the absolute pressure zero point ； A differential pressure gauge measures the difference between two pressures being measured. Gauge pressure meters are classified into vacuum gauges, pressure-vacuum gauges, micro-pressure gauges, low-pressure gauges, medium-pressure gauges, and high-pressure gauges based on their measurement range. Vacuum gauges are used to measure pressure levels below atmospheric pressure ； Pressure vacuum gauges are used to measure pressure values that are lower than or higher than atmospheric pressure ； Micro pressure gauges are used to measure pressure values below 60,000 Pa ； The low-pressure gauge is used to measure pressure values from 0 to 6 MPa ； Medium-pressure gauges are used to measure pressure values ranging from 10 to 60 MPa ； High-pressure gauges are used to measure pressure values above 100 MPa. The casing of the seismic pressure gauge is designed as a fully sealed structure, and it is filled with damping oil; thanks to its damping effect, it can be used in environments where there is vibration or fluctuations in medium pressure (load). A pressure gauge equipped with an electric contact control switch can perform signaling and alarm functions or control functions. Gauge pressure transmitters equipped with remote transmission mechanisms can provide the electrical signals required in industrial engineering (such as resistance signals or standard direct current signals). The isolator (chemical seal) used on diaphragm gauges enables the separation of the medium to be measured from the instrument through a diaphragm, allowing for the measurement of pressure in highly corrosive, high-temperature, or crystalline media. The elastic element of a pressure gauge: In mechanical pressure gauges, the elastic sensing element undergoes elastic deformation as pressure changes. Mechanical pressure gauges use sensitive elements such as Bourdon tubes, diaphragms, bellows, and corrugated tubes, and are classified accordingly. Sensors are generally made of copper alloys, stainless steel, or special materials. Elastic sensitive elements: ??? Bourdon tubes are classified into types such as C-type tubes, coiled spring tubes, and spiral tubes. Cold-work hardening type material billets are generally used; they possess high plasticity in their annealed state, and after pressure processing, cold work hardening, and heat treatment, they acquire high elasticity and strength. Under the action of pressure in the internal cavity, the Bourdon tube utilizes its elastic properties to conveniently convert pressure into an elastic displacement at its free end. The measurement range of a Bourdon tube is generally from 0.1 MPa to 250 MPa. ? ? The diaphragm sensor element is a circular diaphragm with wavy patterns; it is located between two flanges, either welded to the flanges or with its edges held between two flanges. One side of the diaphragm is under the pressure of the medium being measured. The slight bending deformation generated by such a diaphragm can be used to indirectly measure the pressure of the medium. The level of pressure is indicated by the pointer. The diaphragm transmits greater force compared to a Bourdon tube. Since the periphery of the diaphragm itself is fixed, it has good vibration resistance. Diaphragm pressure gauges can provide high levels of overpressure protection (for example, with the diaphragm attached to the upper flange). A protective coating can also be applied to the diaphragm to improve corrosion resistance. Diaphragm pressure gauges can be used to measure media with very high viscosity, those that are dirty, or crystalline, by employing measures such as open flanges, flushing, and openings. The pressure measurement range of diaphragm gauges is 1600 Pa to 2.5 MPa. ?? The diaphragm sensor element consists of two diaphragms with a circular wave-shaped cross-section that are fitted together. The pressure of the medium is applied to the inside of the diaphragm chamber, and the deformation resulting therefrom can be used to indirectly measure the pressure of the medium. The magnitude of the pressure value is displayed by the pointer. Diaphragm pressure gauges are generally used to measure low pressures of gases, and they possess a certain degree of overpressure protection capability. When several diaphragm sensor elements are stacked together, they generate a large transmission force to measure extremely small pressures. The pressure measurement range of the diaphragm gauge is 250 Pa to 60,000 Pa.