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CLASSIFICATION OF PRESSURE MEASUREMENTS
Pressure measurements are relative and therefore refer to a reference pressure. There are four
types of pressure measurement which enable the reference pressure to be defined immediately.
- Absolute pressure (A) – Pressure with respect to absolute zero, the ideal vacuum reference; the
pressure measured is always higher than the reference pressure.
- Gauge (G) – Pressure measured with respect to atmospheric pressure, environment pressure is
the reference; the pressure measured is always higher than the reference pressure.
- Vacuum (V) – Pressure with reference to atmospheric pressure, environment pressure is the
reference; the pressure measured is always lower than the reference pressure.
- Differential pressure (D) – Pressure measured with respect to any reference pressure; the pres-
sure measured may be higher or lower than the reference pressure.
ENGLISH
115
Absolute Relative
(GAUGE)
Differential
Atmospheric
pressure
Zero
pressure
VACUUM
P. to be
measured
Reference
P.
Differential pressure D
Relative pressure (gauge) G
P. to be
measured
Atm. P.
Vacuum
Absolute pressure A
P. to be
measured
The case G is similar to the case D
where the reference P = atmospheric P