McLeod gauge is used to measure absolute pressure from 1 to 10⁶. This type of gauge is generally used to measure high vacuum and these are easy to use its calibration is almost the same for all non-condensible gauges.
McLeod Gauge is filled with some gas and the McLeod gauge assembly rotates periodically by an electric motor. When this gauge returns to its vertical position, the trapped gas is compressed into a smaller volume by the action of mercury. At this pressure, the height of the mercury column in the capillary tube is directly related to the vacuum through the gas flow.
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Advantages and Disadvantages of McLeod Gauge
Advantages
1. The McLeod Gauge is a powerful tool that can measure a gas's pressure.
2. It has advantages, such as being able to measure high pressures accurately and quickly and being able to work in extreme temperatures.
3. It is easy to use and maintain, making it an ideal choice for industrial applications.
4. The McLeod Gauge can be used with different gases without any calibration adjustments required.
5. This makes it extremely versatile and cost-effective for various applications.
Gauge Disadvantages
1. It requires regular maintenance for optimal performance.
2. There are several drawbacks associated with this gauge that need to be considered before using it.
3. The most common disadvantages of the McLeod gauge include its accuracy, sensitivity to temperature changes, and its tendency to become clogged with dirt or other particles.
4. It is also more expensive than other gauges and requires regular maintenance for optimum performance.
The Ionization Gauge Working Principle
The Ionization gauge range of 10³ to 10⁶ mm measures high pressure. It is made up of a tube that is in direct contact with the medium. This tube is made up of a cathode grid and plate. The grid is placed at a high positive relative to the cathode and a current-indicating device is connected to the plate. There is a regular contact current between the grid and the cathode.
Working Principle
The working principle of the Ionization Gauge depends on the number of electrons emitted from the heated filament. When the filament current flows, the electrons coming out of the cathode are attracted toward the grid and then move through the grid toward the plate, due to the collision of the electrons with the gases present in the tube, ions are formed. And the positive ions get collected on the plate.
The amount of ion current is directly proportional to the amount of gas present. The ion current can be measured by an automatic balance potential meter. The electron flow collected on the grid is kept constant by the grid current regulator.
Advantages and Disadvantages
Advantages
1. Ionization gauges are capable of measuring very low-pressure levels, making them ideal for measuring high or ultra-high vacuum conditions.
2. Ionization gauges have a fast response time, making them suitable for dynamic processes or rapidly changing pressure conditions.
3. These gauges are capable of measuring a wide range of pressures, from rough to high vacuum conditions.
4. Compared to other types of gauges, ionization gauges are relatively more numerous and more widely available.
Disadvantages
1. The most common disadvantage of ionization gauges is their sensitivity to environmental factors such as temperature, humidity, and pressure changes. If these environmental factors are not taken into account, the readings obtained from the ionization gauge may be inaccurate.
2. Ionization gauges require a certain amount of maintenance to function properly.
3. This gauge can also be at risk of damage due to improper use or exposure to harsh chemicals or solvents.