Pressure Reference Chart
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Atmospheric / Barometric Pressure |
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Pressure Type: |
Gage |
Absolute |
Vacuum |
Compound |
Elevated |
Sealed Gage |
Differential |
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Pressure Reference: |
Atmosphere Vented |
Vacuum Sealed |
Atmosphere Vented |
Atmosphere Vented |
Atmosphere or Vacuum |
Atmosphere Sealed |
Low Side |
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Definition: |
Units above atmosphere |
Units above full vacuum |
Units below atmosphere |
Units above and below Atmosphere |
Units above an offset |
Units above a sealed reference |
Units between two unknown pressures |
Pressure Reference Definitions
Gage Pressure: Pressure
measured above local ambient atmospheric pressure. Sensor has a
reference that is exposed to atmosphere.Common applications are
Hydraulics, Pneumatics and liquid level.
Sealed Gage Pressure: Gage
Pressure measured above a sealed pressure reference. The reference
pressure is hermetically sealed at some ambient pressure so that the
reference remains static. Used for high pressure applications where
daily atmospheric pressure changes are insignificant relative to the
measured pressure. Common applications are Hydraulics, Pneumatics and
High pressure pumps/compressors.
Vacuum Pressure: Pressure
measured below local ambient atmospheric pressure. Sensor has a
reference that is exposed to atmosphere. Sometimes referred to as
“negative” pressure. The sensor is referenced to atmosphere and the
output (usually) increases as the pressure decreases. Typical
applications are vacuum molding, flow detection and gas sampling.
Absolute Pressure: Pressure
measured above a full vacuum. The sensor reference is evacuated and
hermetically sealed so that it remains static (some manufactures
electronically offset the zero). The most common application is to
measure atmospheric pressure.
Differential Pressure: The
difference between two unknown pressures. Sensor has a high side port
and a low side port and the output is the difference between the two.
Common applications for differential pressure sensors include flow
(across an orifice) and level of a fluid in a sealed container.
Compound Pressure:
Pressure measured above and below local ambient atmospheric pressure.
The reference side of the sensor is open to atmosphere. Application:
Automotive manifold pressure.
Elevated Pressure:
Pressure measured above a reference usually atmospheric (gage) but
could also be a vacuum (absolute) with an artificial (suppressed) zero.
A common application is water tower level measurement where only the
level in the elevated tank is needed not the head pressure in the pipe
leading up to the tank.
Types of sensores
Piezoresistive silicon sensors
non-encapsulated for gasses and dilute, non-aggressive fluids with stainless steel membrane for standard industrial applications
Stainless steel thin film sensors
for hydraulics applications and high dynamic pressure load
Thick-layered ceramic sensors
for aggressive media
Capacitive ceramic sensors
for aggressive environments and very small ranges of measurement
range / full scale output (FSO)
The algebraic difference between finale value and initial value
e.g.: 20 mA - 4 mA = 16 mA
conversion factor
1 mbar = 100 Pa
1 bar = 14,5 PSI
1 PSI = 68,95 mbar
