For thermocouple gauge, it is divided into filament thermocouple gauge and short filament thermocouple gauge according to its technical parameters. Filament thermocouple gauge is one of the earliest low vacuum gauges used in China. The gauge has a simple structure and is easy to use.
Vacuum gauge classification and its applicable range
In pressure measurement, except for a few direct measurements, most of them are indirect measurements. It is to cause certain physical phenomena in the measured gas first, and then measure the physical quantity related to the pressure in this process, and then try to determine the pressure value. This is a characteristic of vacuum measurement and can cause some problems.
1.Vacuum gauge is an instrument for measuring gas or vapor pressure below an atmospheric pressure.
2. A vacuum gauge is an instrument that directly calculates (or obtains) pressure from the physical quantity measured by the vacuum gauge itself.
3. Relative vacuometer is a vacuum gauge that must be calibrated before vacuum degree measurement.
The relationship between any specific physical phenomenon and pressure is only significant within a certain range of pressure, beyond which the relationship becomes weaker. Therefore, any method has a certain measuring range, which is the “range” of the vacuum gauge. It is one of the important contents of vacuum science to extend the range of each method as far as possible. The pressure range involved in modern vacuum technology is up to 19 levels (105 ~ 10-14 Pa). No vacuum gauge can measure such a wide range of pressure, so several kinds of vacuum gauges are always used to manage certain areas. However, due to the difference of various vacuum gauges in principle, large errors are often caused in the connected areas. In order to improve the performance of the vacuum gauge and improve the accuracy of vacuum measurement, the main phenomena must be highlighted and the parasitic phenomena must be suppressed. Table 1 shows the pressure measurement ranges of some vacuum gauges.
At higher pressures (105 ~ 1Pa), pressure differential U-tube manometer, maclau vacuum gauge, film gauge, spring tube manometer, etc. In 103 ~ 10-2 Pa intermediate pressure range, the use of gas properties (heat conduction, viscosity) of the change of the picotorimeter, viscous vacuum gauge. At low pressure, an ionization gauge is used to measure the ionization of gas molecules.