McLeod gauge | Working and Construction | Advantages and Disadvantages | Limitations

By | January 30, 2019

McLeod gauge | Working and Construction | Advantages and Disadvantages | Limitations

Hello friends, today in my this Post I will tell you about the McLeod Gauge and it’s working with it’s advantages and disadvantages.

Basic Information about the McLeod gauge :

The McLeod gauge is for measuring pressures ranging from 0.01 micron to 1 mm of Hg. It operates on the principle of compressing a known volume of low pressure gas to a higher pressure and measuring the resulting change in volume by a mercury manometer.

Fig. McLeod gauge

McLeod gauge
Construction and Working of the McLeod gauge :

The construction of McLeod gauge is shown in Fig.
McLeod gauge comprises a, system of glass tubing made of tough glass and mercury is used to trap the known volume of gas. The gauge is connected to the unknown gas whose pressure is to be measured.

The plunger moves up, lowers the mercury level to the cut off positions entering the gas at unknown pressure. through the tube. This gas fills the tubes down to the cut off position of mercury level. Here the pressure is equal throughout the tubes. Now the plunger is moved down to rise the mercury above the cut-off and traps the gas inside the bulb and measuring capillary. Further pushing of plunger compresses the gas in the measuring capillary and mercury in the reference capillary reaches to zero reference line.
The pressure in the measuring capillary is higher than the measured pressure in reference capillary. This difference in pressure causes the difference in mercury level in two tubes. This difference in height represents the rise in gas pressure and unknown pressure is calculated.

Advantages of the McLeod gauge :

(1) It is very simple in use.
(2) Measurement is independent of gas composition and it is related to physical dimensions of gauge.
(3) It is a very accurate pressure measuring device.
(4) It can be ‘used ‘as a standard to calibrate other low pressure gauges.

Limitations of the McLeod gauge :

(i) If the gas contains the vapour, it may not give correct result.
(ii) It is applicable to those systems where mercury is tolerable. .
(iii) It does not give continuous output.


So, this is all about the McLeod gauge and it’s working with itsi advantages and disadvantages. I hope that every single line of this is understandable to you, and if you liked this Post then please also share it with your friends.


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