Want this question answered?
You can't. There is no atmosphere in a vacuum.
An atmospheric condenser operates naturally at atmospheric pressure (1.013bar). A vacuum condenser operates at pressures below atmospheric and will use some sort of pump to provide a vacuum.
Gauge pressure usually refers to the pressure difference between ambient, atmospheric pressure and the pressure in a vessel or line. A gauge pressure of zero would mean that the vessel or line was at atmospheric pressure. Normally the pressures of interest are ABOVE atmospheric so the gauge pressure is positive. Vacuum gauge pressure measures how far BELOW atmospheric pressure a vessel or line is. As such vacuum gauge pressure may be measured as a negative number - or for convenience it may be reported as a positive number with the caveat that it is "vacuum gauge pressure", meaning that the reported pressure is how far atmospheric pressure is above the pressure in the vessel or line.
The atmospheric pressure on the moon is nearly zero (effectively vacuum).
absolute pressure is calculated from a vacuum (0 psi) and atmospheric pressure is14.7psia or 14.7 psi above a vacuum 1psi on a tire pressure gauge is called 1psig = 15.7psia 10psig=24.7psia 100psig=114.7psia etc.
Do you drive a tractor trailer (semi) with air brakes? where is the air coming from when you notice this. This person's probably talking about a car......It is atmospheric pressure entering the vacuum booster, the air rushing past the valves inside.
To demonstrate atmospheric pressure.
A total vacuum is a space that is completely empty of matter. It is not practically possible to achieve a complete vacuum . An approximation to this is a space with pressure much less than atmospheric pressure.
Condenser Backpressure is the difference between the Atmospheric Pressure and the Vacuum Reading of the Condenser, that is: Backpressure = Atm. Pressure - Condenser Vacuum Pressure Reading Usually, the condenser vacuum pressure is read by a manometer installed at the condenser. The atmospheric pressure is read using a barometer
pressure is usually measured relative to atmospheric this is called gauge pressure. if you compare against absolute zero pressure (vacuum) this is called absolute pressure.
You probably have air in the lines or the brake booster is losing vacuum. Have the brakes bleed and have someone put a vacuum gauge on the booster,
The brakes need to be bled, or is there no vacuum pressure? in that case you need to check all vacuum lines, including the ones for the cabin and other accessories, not just the brakes.