Resistance vacuum gauge is one of the heat conduction vacuum gauges. The pressure is reflected by the change of the resistance of the hot wire. In the process of measuring the change of hot wire resistance, according to the different methods of measuring the change of hot wire resistance, the resistance vacuum gauge can be divided into different modes. Today, EVP vacuum pump manufacturers will work with you to understand these types of resistance vacuum meters.
According to the different measurement methods of hot wire resistance, the resistance vacuum gauge mainly includes three types: constant voltage type, constant temperature type and constant current type.
The constant voltage type indicates the corresponding pressure change by keeping the voltage at both ends of the equipment bridge unchanged and observing the relationship between the unbalanced current and the pressure. In the process of measurement, the voltage is fixed, when the pressure in the gauge fluctuates, the heat conduction will change, and the temperature of the hot wire will also change, so that the resistance will change and the bridge will lose balance. The indicating instrument can read the change of pressure and give the specific relationship between current value and pressure through calibration curve. This type of resistance vacuum gauge is very difficult to measure the pressure above 133pa. Generally, the measuring range is between 133pa and 1.33 × 10 ^ – 1pA.
In the measurement process of constant temperature (constant resistance) resistance vacuum gauge, the relationship between bridge voltage and pressure is taken as the approval curve. In the process of realization, the resistance and temperature of hot wire are basically fixed. When the pressure changes, when the temperature and resistance of the hot wire change, the bridge will be restored to balance by adjusting the voltage, so that the temperature and resistance of the hot wire will be restored to the original value. This type of resistance vacuum gauge has a short response time, and its measurement range is generally between 10 ^ – 1pA and 1 × 10 ^ 4pa.
The constant current type resistance vacuum meter keeps the hot wire current (or bridge current) unchanged, and then observes the relationship between the unbalanced voltage and the pressure. In the process of pressure change, the temperature change of this kind of hot wire is very violent. Therefore, it is necessary to limit the maximum working temperature to prevent hot wire damage and ensure the working stability of the equipment in the full range.
The three types of resistance vacuum meters are widely used in practice, the constant voltage type and the constant temperature type.
Resistance vacuum gauge is a vacuum gauge made by using the principle of gas thermal conductivity and gas pressure. The electric bridge is used to measure the resistance change in vacuum to convert the vacuum degree. Resistance vacuum gauge, also known as piezometer (Pirani), adopts zj-52 resistance gauge. The vacuum metering range is wide and the drift is small. It is suitable for vacuum measurement and control of vacuum equipment.