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. Influence oxygen of 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. The influence vapor of vapor is to be able to coagulate sexual gas, compress the gas that be measured should be compressed when type vacuum gauge is measured, make vapor condenses, because this is in,cannot use usually compress type vacuum gauge to undertake metrical. The influence that it conducts vacuum gauge to heat and oxygen are same, can make compasses canal zero shift changes with sensitivity happening. The material of filament of plan compasses canal is resistor vacuum gauge and ionization of tungsten cathode hot cathode tungsten, tungsten filament temperature is higher, high temperature filament and vapor produce oxidation, vapor can be decomposed by surface of high temperature tungsten and with tungsten reaction generates oxidation tungsten and atomic condition hydrogen, after oxidation tungsten evaporates, adhere to go up in wall of compasses canal Bo. Atomic condition hydrogen captures in the oxidation tungsten from tube wall oxygen becomes vapor again. Such loops go down, vapor is removing ” to carry the action of ” tungsten. Cause tungsten cathode to evaporate ceaselessly, and make filament damages quickly. Especially vapor cent is pressed be more than 10^{- 2}When Pa, the life of compasses canal is very brief, use not easily at measuring vapor. Connecting general reason condition to fall. Can use U form to the measurement of vapor manometric with exert of vacuum gauge of filmy compasses, radiate, compasses sticking sluggish, gram Ceng Zhen is empty plan etc. Canal of cold cathode compasses won't produce oxidation problem, also can use at vapor to divide those who control expensive vacuum system to measure. The influence of oily steam is using the bleed system that has oil (mechanical pump, oil diffuses pump) when bleed, the organic oily steam with the much existence in the system reachs its division other people, their vapour pressure is lower, because this cannot be used,compress type vacuum gauge to undertake metrical. When if use,compressing type vacuum gauge to measure the ultimate pressure of mechanical pump. The data that should measure than conducting vacuum gauge with heat is tall quantitative class. The U that use oil manometric when measuring oily steam. Because working oil is OK and deliquescent oily steam, also cannot receive correct instruction so. When conducting vacuum gauge or ionization vacuum gauge to measure oily steam with heat. Because oil steam pollutes filament or the meeting is decomposed on high temperature cathode generate a hydrocarbon, pollute electrode and tube wall badly, make heat conducts circumstance change, and make the sensitivity of compasses canal and character produce apparent change, cause measure an error. In oily vapour cent controls expensive system in, with film vacuum gauge is measured when low vacuum; Radiation is used when high vacuum
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