For measuring relatively shallow rarefactions intended compound. In principle they do not differ from the usual mechanical gauges. To connect such a device, install a pipe rupture standard pneumatic T-adapter, which can withstand the required vacuum and to it, similar to a manometer, connect the pressure-vacuum gauge, designed for the required span. Verify tightness of all joints. Note that some devices of this type indicate the absolute value of pressure in the pipeline (as it is below zero), and the other is a relative (as it is below atmospheric).
At lower pressures and inert atmosphere in the pipe use a sensor, the principle of which is based on the temperature change of the filament lamps exposed to gas molecules. They are withdrawn from filament heat, with the result that it cools, its resistance decreases. In any case, do not turn the power of such a device, when the pressure is equal to or close to atmospheric and the system is the air.
With deep vacuum small pressure changes have little effect on the temperature of the filament. In this case, use the special electrometer lamp. Their principle of operation is based on the fact that the molecule of any gas is much larger than the electron, so the space is less than such molecules, the easier it is for electrons to fly through it. In fact, it is a vacuum diode, which is not sealed and is pneumatically connected to a vacuum system. Under other equal parameters with increasing depth vacuum its resistance decreases. Such a device also cannot be included in the absence of a vacuum, and it is always better to maintain in the system the negative pressure. The separation of the sealing process of the container from the carry out only immediately prior to accession.
For the transfer of absolute pressure values in a relative vacuum level and Vice versa use the following formulas:P Rel=P ATM-P abs: P abs=P ATM-P usdes P abs - absolute pressure in the vacuum system, P Rel is the relative value of the vacuum, P ATM is the atmospheric pressure. They must all be expressed in the same units.