Vacuum gauge of principle and measuring range
Vacuum refers to the state of gas below one atmospheric pressure in a given space, which is a physical phenomenon. In vacuum technology, vacuum refers to the atmosphere. Generally, it means that part of the material in a specific space is discharged, so that its pressure is less than a standard atmospheric pressure. We generally call this space a vacuum or vacuum state. Pascal, Torr and mbar are commonly used as pressure units for vacuum.
Classification of vacuum:
Front vacuum: 1 * 10 Torr~1000 Torr
High vacuum: 1 * 10Torr~10Torr
Ultra high vacuum: below 10 ° Torr
Vacuum gauge (also known as vacuum gauge and vacuum gauge) is an instrument for measuring vacuum degree or low pressure. Generally, it is used to measure the pressure by using the change of some physical effect of gas under different pressure. It is widely used in scientific research and industrial production. According to the different physical mechanisms used in the measurement principle of vacuum gauge, the main vacuum gauges can be divided into three categories
They are vacuum gauges that use mechanical properties and gas dynamics effects to use charged particle effects.
Typical vacuum gauges using mechanical properties include Bourdon gauge and capacitance film gauge. Typical vacuum gauges using aerodynamic effects include Pirani resistance gauge, thermocouple gauge and heat conduction gauge;
Typical vacuum gauges using charged particle effect include hot cathode ionization gauge and cold cathode ionization gauge.
Types of vacuum gauges on the market
Vacuum gauge+vacuum gauge (vacuum gauge controller): to be used together.
Vacuum transmitter (vacuum gauge): the body integrated circuit part can output various models
The customer can choose the two forms according to the actual application. The vacuum gauge and controller are mainly used in some harsh field environment or early integrated equipment. They are composed of regulation, cable and controller. The initial cost is slightly higher. The typical advantage is that the vacuum gauge is cheaper to replace in the later maintenance; With the development of industrial automation, vacuum transmitter (vacuum gauge) has become the main product of vacuum measurement, and corresponding communication products can be selected according to the signal (digital/analog) that can be processed on site.
Capacitive film pressure gauge, which is independent of the gas component and mainly affected by the ambient temperature (temperature compensation), is the most accurate equipment for measuring differential or all gas pressures (including steam condensation and the environment with irregular operating temperature). At present, the maximum measuring pressure of the known product is 25000 Torr and the minimum measuring pressure is about 10 Torr. Most of the accuracy is 0.25% of the reading, of which the high accuracy is 0.08% – 0.025%. The measurement range span generally has 4 orders of magnitude or 5 orders of magnitude.
Application:
1.Semiconductor industry etching, employed by CVDPVDAL
2.Photovoltaic industry, PECV, etc
3.LCD manufacturing equipment
4.Industrial vacuum equipment, standard vacuum gauge
5.National defense research and application
Thermocouple vacuum gauge
The filament is heated by a constant current source. Since the gas particles collide with the resistance wire and take away the energy, the temperature of the resistance wire will change. The filament temperature changes from the thermocouple voltage (constant voltage), and the pressure is calculated according to the voltage change.
The energy loss of the hot wire is proportional to the gas concentration and gas composition around the hot wire)
Measured pressure range: 10Torr to 10Tor
Application:
1.Front vacuum measurement, such as front vacuum pump, coating, photovoltaic, plasma industry
2.Medium and low vacuum measurement industry, such as metallurgy
3.Interlock control of high vacuum gauge
Pirani Vacuum Gauge
The filament is heated by a constant current source. Since the gas particles collide with the resistance wire and take away the energy, the temperature of the resistance wire will change (constant temperature), causing the bridge (Wheatstone resistance) to change. The pressure is calculated according to the resistance change.
The energy loss of the hot wire is proportional to the gas concentration and gas composition around the hot wire)
Measured pressure coverage: 100Torr to 10Tor (refer to actual product indicators for details)
Application:
1.Front vacuum measurement, such as front vacuum pump, coating, photovoltaic, plasma industry
2.Medium and low vacuum measurement industry, such as metallurgy
3.Interlock control of high vacuum gauge
Convectron&Convection Vacuum Gauge
The vacuum gauge has the same structure as Pirani, and its pressure measurement is based on the heat loss rate of the sensor wire. Unlike the traditional thermocouple gauge and Pirani vacuum gauge, which only use conductivity loss, heat loss makes the vacuum gauge fully use heat loss due to the use of convection heat dissipation at high pressure. The quantity range extends to the atmospheric end.
Measuring range: 10torr to atmospheric pressure, with higher accuracy than general Pirani vacuum gauge
Application:
1.Front vacuum measurement, such as front vacuum pump, coating, photovoltaic, plasma industry
2.Medium and low vacuum measurement industry, such as metallurgy
3.Interlock control of high vacuum gauge
There are many kinds of vacuum gauges, including compression vacuum gauge, ionization vacuum gauge, thermocouple vacuum gauge, resistance vacuum gauge, etc. Vacuum measurement of vacuum gauge is an important part of vacuum technology, so vacuum gauge is widely used in scientific research and production. So what factors should we consider when choosing vacuum timing?
1.Different vacuum gauges have different measuring ranges and measuring accuracy. First, ensure that the measuring range of the vacuum gauge meets the needs of the equipment, and then consider the measuring accuracy of the vacuum gauge;
2.Some vacuum gauges have requirements for the measured gas. For example, the cathode of the hot cathode ionization vacuum gauge is vulnerable to the damage of excessive air, pump oil vapor and other pollutants, so it is necessary to consider whether the measured gas will cause damage to the vacuum gauge;
3.Some vacuum gauges will affect the measured environment. For example, the measured gas will be compressed when the compressed vacuum gauge is measuring, which will cause water vapor to condense. Therefore, it is necessary to consider whether the vacuum gauge will affect the measured vacuum environment;
4.Consider whether the pressure measured by the vacuum gauge is full pressure or partial pressure, whether it has been calibrated, and whether it is related to the gas type;
5.Consider whether the vacuum gauge can realize continuous measurement, numerical indication and reaction time;
6.Consider the stability, reliability and service life of the vacuum gauge.
7.Consider the installation method, operation performance, warranty, management, market availability, ease of purchase and specifications of vacuum gauge
If possible, kindly suggest please your working industry/process, working pressure, working medium, etc. Given detailed request helps to gain better-matched customized solution. Thanks for your patience.
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