The working principle of the pvd coating machine vacuum gauge, the ionization vacuum gauge is a vacuum gauge that obtains the pressure by ionizing the gas molecules and measuring the number of ions (current). The measuring vacuum is above 10-8 Pa, and it is widely used in the field of high vacuum to ultra-high vacuum, with excellent quantitative performance.

 The ionization vacuum gauge can be divided into two kinds according to different ionization methods: one is the most widely used hot cathode ionization vacuum gauge that works on the principle of hot electron emission at high temperature cathode; The other is a cold cathode ionization vacuum gauge that works by using the principle of high voltage discharge in vacuum.
The electrons that ionize the gas molecules in a hot cathode ionization gauge are obtained by heating the filament. There is a certain limit for measuring vacuum degree with hot cathode ionization vacuum gauge. When hot electrons hit the anode mesh, they emit soft X-rays. The ion collector emits photoelectrons after soft X-ray irradiation. The emitted photoelectrons and ions have the same incident effect, which is called the pseudo-ion current, so the vacuum gauge has a residual current independent of pressure, which misevaluates the actual vacuum degree. The schematic diagram of residual current generation is shown in Figure 2. In addition, the gas molecules adsorbed on the anode network will also be detected as ions after being impacted by electrons, which also interferes with the measurement accuracy of the vacuum gauge.
Cold cathode ionization vacuum meters utilize the phenomenon of high voltage discharge in a vacuum, also known as cold gauge. The cold cathode emits fewer electrons than the hot cathode, and the voltage is simply added between the Yin and Yang poles, if the pressure is lower than 0.1Pa, it will not continue to discharge. By applying a magnetic field from the outside, the distance of the electrons can be increased to achieve continuous discharge at a lower pressure.
The electrons released from the cathode are helical in motion by the Lorentz force and are bound in the magnetic field. The spiral motion greatly increases the distance the electrons travel. The electrons are eventually captured by the anode, but collide with the gas molecule several times before being captured, creating a plasma state between the two cathodes. The electrons in the plasma and the electrons released by the cathode will make spiral motion, but the cation is caught by the cathode in a short time because of its larger mass and larger spiral motion radius, and produces secondary emission electrons. The electrons produced by gas ionization and the secondary electrons emitted by the cathode also move between the cathode plates for a long time, so that the ionization process continues in a chain.
Cold cathode discharge can occur at a pressure of 0.1Pa. The number of ions captured at the cathode is directly proportional to the pressure and the ionization cross-section area of the gas molecules. If the proportional coefficient of ionic current and pressure is known, the pressure value can be known. The ionization section area varies according to the gas molecules, and the proportion coefficient also varies according to the gas molecules. Vacuum gauges on the market generally measure the proportion factor with dry air or nitrogen as the standard.
The cold cathode ionization vacuum gauge of pvd coating machine has stable measuring performance and can be used in high vacuum field. At the same time, because it is a cold cathode ionization mode, there is no need to worry about the burning of the electrode.
The disadvantages of a cold cathode ionization gauge are:
(1) The stability of discharge is insufficient;
(2) The amount of electrons emitted from the cathode is seriously affected by surface contamination;
(3) The vacuum gauge itself has a strong magnetic field, and it is necessary to consider the location of its installation on the equipment.