Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges
A manometer is a pressure measuring instrument, usually limited to measuring pressures lower than atmospheric. It is often used to refer specifically to liquid column hydrostatic instruments.
A vacuum gauge is used to measure the pressure in a vacuum, which is broadly divided into two categories: high and low vacuum (and sometimes ultra-high vacuum). Many of the different techniques used to measure these categories have an overlap at some point in the pressure range. By combining several different types of gauge it is possible measure system pressure from 10 mbar down to 10e-11 mbar.
A manometer is a pressure measuring instrument, usually limited to measuring pressures lower than atmospheric. It is often used to refer specifically to liquid column hydrostatic instruments.
A vacuum gauge is used to measure the pressure in a vacuum, which is broadly divided into two categories: high and low vacuum (and sometimes ultra-high vacuum). Many of the different techniques used to measure these categories have an overlap at some point in the pressure range. By combining several different types of gauge it is possible measure system pressure from 10 mbar down to 10e-11 mbar.
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Last Updated: June 16, 2007
Last Updated: June 16, 2007
What is a Pressure Transmitter?
Pressure measurements may be expressed relative to various zero references.. Absolute pressure of a fluid is referenced against a perfect vacuum. Gauge pressure is referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Atmospheric pressure is typically about 100 kPa, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For gauge pressures several times larger than atmospheric pressure, this variation is small as a percentage of reading and may be ignored. Differential pressure is the difference in pressure between two points.
Examples of absolute pressure measurements include barometric pressure, altimeters, and the Manifold Absolute Pressure (MAP) sensor used in the engine control systems of modern fuel-injected automobiles. Examples of gauge pressure measurements include the tire-pressure gauge and sphygmomanometer. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings.
Gauge pressure of vacuum is usually indicated and expressed without a negative sign, so it is equal to the atmospheric pressure minus the absolute pressure.
Examples of absolute pressure measurements include barometric pressure, altimeters, and the Manifold Absolute Pressure (MAP) sensor used in the engine control systems of modern fuel-injected automobiles. Examples of gauge pressure measurements include the tire-pressure gauge and sphygmomanometer. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings.
Gauge pressure of vacuum is usually indicated and expressed without a negative sign, so it is equal to the atmospheric pressure minus the absolute pressure.
