When using vacuum gauge to measure the pressure of rare gas, not only general and commonly used opposite vacuum gauge and sort of the gas that be measured are concerned. And the gas of different sort is different also to the influence of vacuum gauge. If be measured,gas is nitrogen or inert gase, do not have an influence basically. But below most circumstance, the gas in vacuum system is the different combination of a variety of gas such as nitrogen, oxygen, hydrogen, vapor, firedamp, oily steam and steam, among them especially the group branch such as oxygen, vapor, oily steam gives canal of vacuum gauge compasses to bring very big impact. Because this is when choice vacuum gauge, need considers composition of the gas that be measured to reach the effect that measures accuracy to bring to the life of compasses canal.

Aerobic influence

Oxygen is ideal gas, can undertake metrical with vacuum gauge of wheat family name, but when oxygen when cent pressing is exorbitant, can make mercuric surface produces oxidation, affect mercuric exterior tension, make mercury is in capillary in the position when shift is not exact, cause measure an error.

Common heat is conducted (exemple resistor) the filament of vacuum gauge can oxidize below high temperature, change the exterior position of heater, cause compasses valve the change of zero shift and sensitivity, should use the compasses pipe that fights oxidation heater. Yi Yi of filament of compasses of hot cathode ionization oxidizes, make its loss of life.

To oxygen cent presses taller aeriform atmosphere, usable inside limits of thick low vacuum filmy vacuum gauge is measured; Radiation vacuum gauge and pipe of cold cathode compasses are used when high vacuum.

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