A compound pressure gauge measures two scales, one in positive pressure and one in negative (below atmospheric) pressure or vacuum
positive pressure is measured in pounds per square inch (psi)
or kilopascals or in some cases bars (1 bar = 14.35 psi) [ the average atmospheric
pressure at 1000 feet above sea level]
vacuum is measured in millimeters of Mercury mmHg or inches of mercury inHg
Pisa micron
i need to explain what an absolute pressure gauge measures
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.
Bourdon's tube pressure gauge cannot be used to measure negative pressure. This is because absolute pressure must be measured and the Bourdon gauge only indicates the gauge pressure.
Psig (pound-force per square inch gauge) is a unit of pressure relative to atmospheric pressure at sea level. By contrast, psia measures pressure relative to a vacuum (such as that in space). Most pressure gauges, such as tire gauges, are calibrated to read zero at sea level, because most applications require the difference of pressure. At sea level, Earth's atmosphere actually exerts a pressure of 14.695948804 psi. If a pressure gauge is calibrated to read zero in space, then at sea level on Earth it would read 14.695948804 psi. Thus a reading of 30 psig on a tire gauge, represents an absolute pressure of 44.695948804 psi.
There are a number of different sets of data, in which '8 gauge' occurs. In the British system, a number 8 SWG (standard wire gauge) measures 4.064 mm. In a US system, a number 8 AWG (American Wire Gauge) measures 3.264 mm. There are also sheet steel gauges which differ from the above, and wire gauges for musical instruments have different definitions again. Different again, are the gauges used for hypodermic needles. It is vital to specify which gauge system you use.
The Compound Gauge measures above and below atmospheric pressure (in psig and inches of mercury).
i need to explain what an absolute pressure gauge measures
pressure and temperature
A pressure gauge simply measures and visibly indicates pressure in a system . It does not reduce the pressure. For that you need a PRV (pressure reduction valve ).
A pressure gauge measures blow, a vacuum gauges measures suck
A compound gauge is a pressure gauge that displays both negative and positive gauge pressure measurements. Gauge pressure is a measurement of pressure relative to ambient pressure. For example, if ambient pressure was 14.7 PSI and you were to measure absolute vaccum using a compound gauge, the gauge would indicate -14.7 PSI.
Because Pressure gauge measures the the differenceof pressure so it is called pressure gauge not meter.
Gauge pressure is what you get when you take the reading from your tire pressure gauge. Absolute pressure is the pressure inside your tires plus the atmospheric pressure, which is roughly; 14.7 psi, 101.3 kPa (kilo-Pascals), or one atmosphere. Absolute pressure measures all of the pressure on your tires, inside and out, whereas gauge simply measures the pressure inside the tire.
On a manifold gauge set, there are two gauges. The gauge encased in red measures pressure on the high pressure (discharge) side. That's the "high side gauge". The other will be incased in blue, and measures vacuum pressure on the low side.
It's usually just called a "pressure gauge", the assumption being that you know, or a label on it tells you, that it is measuring water-pressure.
A tool that measures air pressure in a tire or going through a pipe is called an air pressure gauge.
tyre pressure gauge.