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Things to Consider when Measuring Pressure
General
MC5P can measure pressure with its internal pressure modules, or
with external pressure modules. If a barometric module is present,
the measurement results of other modules can be shown either as
absolute pressure or as gauge pressure.
Pressure Type
Every pressure measurement is in fact a pressure difference mea-
surement: a given pressure value is compared against a reference
pressure. In certain cases the reference pressure has a special
meaning (like the atmospheric pressure) and the pressure mea-
surements with reference to against these points are given a spe-
cial name:
•
Absolute pressure measurement
uses vacuum as the refer-
ence pressure.
•
Barometric pressure
(or
atmospheric pressure
) is the ab-
solute pressure of the surrounding atmosphere. It is specially
titled because of its importance.
•
Gauge pressure measurement
uses the atmospheric pres-
sure as the reference. Gauge pressure may be zero, negative
or positive. Most of MC5P’s pressure modules actually mea-
sure gauge pressure although they may be used for measur-
ing other pressure types too.
•
Differential pressure measurement
requires a special dif-
ferential pressure module that has an input available for both
the reference pressure and the given pressure.
To be able to measure absolute pressure with MC5P’s gauge pres-
sure modules, you need a barometric pressure module. Certain
high pressure modules may approximate absolute pressure mea-
surement by adding an entered barometric pressure to the mea-
sured gauge pressure.
MC5P may use two standard pressure modules to measure differ-
ential pressure: One module measures the reference pressure and
another the given pressure. The pressure difference is calculated
by subtracting the reference pressure from the given pressure. More
of this in Part B, chapter
Special Measurements
.
Always ensure that the pressure type setting of your pressure
measurement is what you intended it to be. The pressure type
setting is crucial for getting meaningful pressure measurement
results.
Additional Information
Summary of Contents for MC5P
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