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Environmental Corrections
The deadweight tester has been calibrated to the Gravity, Temperature, and Air Density
stated on the certificate.
Equations and factors are given on the certificate to adjust for any variations in these
environmental conditions.
Gravity
Gravity varies greatly with geographic location, and so will the deadweight tester
reading.
Due to the significant change in gravity throughout the world (0.5%), ensure that the
tester has either been manufactured to your local gravity, or that you have applied the
correction from the calibrated gravity.
Example:
Deadweight Tester calibrated gravity
(980.665 cm/s² is the International Standard Gravity)
Gravity at site
Indicated Pressure
The ability to determine the local gravity value will depend on the data available in the
country that the instrument is to be used in. Some countries have geographic/geological
survey/mapping organizations that have the data readily available. If not, the countries'
National Standards Laboratory may be able to recommend a source of suitable
information.
Temperature
Temperature and Air Density variations are less significant than gravity.
Variations should be corrected for when maximum accuracy is required.
Temperature variation example:
Deadweight Tester calibrated temperature
Operating temperature
Percentage change per °C
Indicated Pressure
TRUE
PRESSURE
TRUE
PRESSURE
=
TRUE
PRESSURE
250
TRUE
PRESSURE
980.665 cm/s²
981.235 cm/s²
250 psi
981
.
235
=
x
250
980
.
665
=
250
.
1453
psi
20°C
24°C
0.002%
250 psi
(
)
. 0
002
+
−
20
24
x
x
100
=
249
.
98
psi
General Information
Environmental Corrections
250
1
1-5
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