GE SF6 Instruction Manual page 35

Pressure measurement
Effective pressure ?
Absolute pressure ?
07- 2016
Description and operation
SF gas monitoring
6
Absolute pressure = effective pressure + atmospheric pressure
Pressure Description
The pressure of SF
ured by of a standard pressure
gauge with a deformable dia-
phragm actuating an indicating
pointer.
One surface of the diaphragm is
in contact with the SF
the other is in contact with the
Effective
atmosphere.
between the gas and the atmo-
sphere is thus measured, taking
atmospheric pressure as a refer-
ence. This is the measurement of
the effective pressure of the SF
gas.
If the deformable diaphragm, one
surface of which is in contact with
the SF gas, blocks a volume
6
where a vacuum has been
developed, the pressure gauge
measures the pressure differ-
ence between that of the SF
and the vacuum. Since the latter
is zero, the pressure gauge
measures the absolute pressure
of the gas.
The absolute pressure of the SF
gas, independent of atmospheric
pressure, reflects the quantity of
Absolute
gas introduced into the compart-
ment and hence its density at the
present temperature.
This is measured by means of an
absolute pressure gauge which
is less generally used and more
delicate than a effective pressure
gauge. This is the reason why a
effective pressure gauge is used,
provision being made for correc-
tions required by atmospheric
pressure
from atmospheric disturbances
and differences of elevation.
GE Information
gas is meas-
6
Standard pressure gauge
gas, while
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The difference
6
Atmospheric pressure
gas
6
6
Vacuum volume
variations resulting
Diagram
SF
6
Absolute
pressure gauge
SF
6
L20- 001EN/08
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