P3800 Series
Users Manual
6-2
Temperature and Gravity Corrections
Deadweight testers are manufactured to give an accurate pressure reference at the
specified temperature and gravity values indicated on the certificates. The following
Standard Values are applied during calibration unless otherwise requested during
manufacture (see Certificate).
Standard Gravitational acceleration (
G
) 9.80665 m/s²
Standard Temperature (T) 20°C
(
)
(
)
G
g
t
T
a
P
P
−
+
=
1
2
1
Where:
1
P
= Corrected
Pressure
2
P
= ACTUAL
PRESSURE
α
= Coefficient of Linear Expansion
(The value for a specific piston / cylinder assembly (PCU) is
shown on the Calibration Certificate)
T
= DWT calibrated temperature (°C)
t
= Temperature at position of DWT (°C)
g
= Gravitational acceleration at position of DWT
G
= DWT calibrated gravitational acceleration
The value of gravitational acceleration (
g
) varies with latitude, height above sea level
and geological conditions at the location of the DWT. When the gravitational
acceleration varies from that for which the DWT was calibrated, the above correction
must be made. The local value of gravitational acceleration (
g
) can be obtained as
follows:
Data from the appropriate geophysical authority
Approximated from the Nomogram.
Calculated from the formula:
(
)
H
L
L
g
0000038086
.
0
2
sin
0000059
.
0
sin
0053024
.
0
1
7803184
.
9
2
2
−
−
+
=
Where:
L
= geographical latitude,
H
= height above sea level in meters and units of g are m/s²
Height Corrections
Tests carried out at locations other than the test stations may require corrections for fluid
heights. The pressure exerted by a column of fluid 1” / 25.4 mm high will not exceed
0.036 psi / 0.0025 bar using the recommended fluids.
1.800.561.8187
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.ca
