Absolute, relative and differential pressure


Pressure is a force that is evenly distributed over a surface. A distinction is made between three measured variables for pressure, which differ in their reference points: absolute pressure, relative pressure and differential pressure.

Absolute pressure

Absolute pressure is measured in relation to absolute vacuum, zero pressure. Here, the pressure is measured in comparison to a vacuum that is enclosed in a sensor element. Absolute pressure gauges only have one connection.

Areas of application for absolute pressure sensors:

  • In the meteorological measurement of air pressure in barometers and altimeters
  • When vacuum packaging food, ensuring that the same vacuum is always applied

Gauge pressure

Relative pressure is measured in relation to the surrounding atmosphere. Relative pressure gauges, like absolute gauges, have a pressure connection. Thus, the sign of a relative pressure can be either positive or negative.

Positive gauge pressure is when atmospheric pressure is less than absolute pressure. Negative overpressure is defined by the exact opposite.

Areas of application for relative pressure sensors:

  • The tire pressure check measures the excess pressure relative to the ambient temperature
  • With medical suction devices (for mucus or secretions), whereby a vacuum is generated by means of a pump

Differential pressure

Differential pressure describes the pressure difference between two pressures. To make this possible, differential pressure gauges have two pressure connections. As with the relative pressure gauges, positive and negative vacuums can be generated. The differential pressure gauge can be used as a relative pressure gauge at any time if you leave a pressure connection open.

Areas of application for relative pressure sensors:

  • In medical technology, the pressure drop is measured to determine a respiratory or gas flow when the container (lung, pipe, hose) narrows the respiratory or gas flow.
  • Filter monitoring devices work in the same way
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