Conversion of relative vacuum and absolute vacuum
The “vacuum degree†commonly used in the international vacuum industry is also the use of absolute pressure mark for zui science; it refers to “extreme vacuum, absolute vacuum, absolute pressureâ€, but “relative vacuum†(relative pressure, vacuum gauge pressure, Negative pressure) Because of the simple measurement method, the measurement instruments are very common, easy to buy and inexpensive, they are also widely used. In theory, the two can be converted to each other. The conversion methods are as follows:
Relative vacuum = absolute vacuum (absolute pressure) - pressure at the measurement site
A standard atmospheric pressure 1atm=101325Pa=101.325kPa=0.101325MPa≈0.1MPa single-turn spring tube pressure gauge (such as Y-100) measures relative pressure, the pointer changes clockwise, and the starting point 0 represents an atmospheric pressure of 0.1MPa, such as The indication is 1 MPa, which means 1 MPa higher than atmospheric pressure and the absolute pressure should be 1.1 MPa. The single-turn spring tube vacuum gauge (such as Z-100) measures the relative pressure. The pointer changes counterclockwise. The starting point 0 represents an atmospheric pressure of 0.1 MPa. If the indicator number is Px (should be a negative value), the absolute pressure P= Px + 0.1 MPa. For example, the indicator number is Px=-0.02 MPa=-20 kPa=-20000 kPa, and the absolute pressure P=Px+0.1 MPa=80 kPa. The indicated number is Px = -0.04 MPa = -40 kPa = -40,000 kPa, and the absolute pressure P = Px + 0.1 MPa = 60 kPa. The indicated number is Px = -0.06 MPa = -60 kPa = -60,000 kPa, and the absolute pressure P = Px + 0.1 MPa = 40 kPa. The indicated number is Px=-0.08 MPa=-80 kPa=-80000 kPa, and the absolute pressure P=Px+0.1 MPa=20 kPa.
Relative vacuum pressure -0.1MPa, the actual should be -0.101325MPa, equivalent to an absolute pressure of 0, which is impossible to achieve, the current high vacuum of Zui can be achieved is about 10^(-12)Pa.
Commonly used vacuum units are Pa, Kpa, Mpa, atmospheric pressure, kilograms (Kgf/cm2), mmHg, mbar, bar, PSI, atm, and the like. The approximate conversion relationship is as follows:
1MPa=1000KPa
1KPa=1000Pa
1 standard atmospheric pressure = 100KPa = 0.1MPa (approximate value, approximate calculation when the demand is not high, for rough calculation)
1 standard atmospheric pressure = 1 kg (Kgf / cm2) (approximate value, used for rough calculation) = 760mmHg
1 standard atmospheric pressure = 14.5 PSI (approximate value, used for rough calculation)
1KPa=10mbar
1bar=1000mbar
1atm=101325Pa (atm means a standard atmospheric pressure as a reference)
Relationship of various parameters
Relationship between pressure, absolute pressure, gauge pressure, vacuum, vacuum pressure, and standard atmospheric pressure
Air pressure can be measured by pressure, gauge pressure, and vacuum.
Absolute pressure: The pressure value with the absolute vacuum as the starting point. It is generally necessary to mark "ABS", or Pabs, in the lower right corner of the symbol indicating absolute pressure.
Gauge pressure: A pressure value above the local atmospheric pressure. The pressure value measured by the pressure gauge is the gauge pressure. The symbol indicating the pressure of the table is generally not marked. If necessary, it can be marked with “e†in the lower right corner, ie Pe. The gauge pressure will change due to changes in local atmospheric pressure.
Vacuum: pressure value below local atmospheric pressure
Vacuum pressure: The difference between absolute pressure and atmospheric pressure. The vacuum pressure is numerically the same as the vacuum, but should be preceded by a minus sign.
The relationship between pressure, absolute pressure, gauge pressure, vacuum, and vacuum pressure is shown in the figure below:
A standard atmospheric pressure is defined as: a temperature of 0 ° C, a latitude of 45 degrees, the sea level is called 1 atmosphere, and the value of the mercury barometer is 760 mm of mercury column height.
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