The ionization vacuum gauge is a vacuum measuring instrument based on the principle that the pressure of the gas to be measured is proportional to the ion flow produced by gas ionization under certain conditions.
The utility model is composed of a cylindrical collector, a grid and a filament in the center of the grid, and the cylindrical collector is outside the grid. The hot cathode emits electrons to ionize the gas molecules, and the ions are collected by the collector. The vacuum gauge measures the gas pressure according to the collected ion current.
Ionization vacuum gauge of principle
In a strong gas with low pressure, the number of positive ions produced by ionization of gas molecules is directly proportional to the gas pressure. The ionization vacuum gauge is a vacuum measuring instrument based on the principle that the pressure of the gas to be measured is proportional to the ion flow produced by gas ionization under certain conditions.
According to the different methods of ion generation, the vacuum gauge which uses the hot cathode to emit electrons to ionize the gas is called the hot cathode ionization vacuum gauge. The measuring instrument consists of regulating working power supply, emission current regulator, ion current measuring amplifier and other parts. The hot cathode ionization gauge is connected with the vacuum system under test. The hot cathode ionization gauge is a triode with cathode, grid and collector. The collector potential is relative to the cathode negative potential and the grid is relative to the cathode positive potential. When the ionization gauge is electrified and heated, the cathode emits electrons. In the process of electrons arriving at the grid, they collide with gas molecules and produce ionization phenomena of positive ions and electrons. When the emission current is constant, the number of positive ions is proportional to the pressure of the measured gas.
After the positive ions are collected by the collector and amplified by the measuring circuit, the vacuum degree to be measured can be read out by the indicator meter.
After the vacuum system is exposed to the atmosphere, the ionization gauge glass bubble and electrode surface will absorb a lot of gas. In the vacuum environment, the gas is released again, which affects the measurement accuracy. In order to eliminate this effect, the gauge must be degassed before measurement. The method of baking is adopted for degassing the ionization gauge tube, that is to say, the filament and grid can be electrified and heated respectively, while the plate adopts high frequency induction heating or electron bombardment to release the gas before measurement. Generally, the ionization vacuum gauge has degassing function. When the true void is greater than 1 × 10 ^ – 2PA, degassing shall be carried out for the ionization gauge according to the requirements of the instructions.