Applying Pressure Corrections - Fluke P5521 User Manual

Applying Pressure Corrections

For ease of operation, the liquid separator is designed to be mounted directly to the test
port on a deadweight tester. This creates an additional head of fluid above the pressure
reference level on the deadweight tester, which means that 0.15 psi / 0.1 bar
(or equivalent) should be deducted from the reading of the deadweight tester to maintain
accuracy.
The flexible diaphragm will be displaced from the center of the chamber during normal
operation, but its elastic properties will always tend to try to return it to central, neutral
position. This "spring" effect exerts a small force on the fluid. As there is no way to
determine the diaphragm's position relative to the center of the chamber at any given
time, a "diaphragm rating" uncertainty of ± 0.15 psi / 0.1 bar (or equivalent) should be
applied to the pressure reading to maintain accuracy.
Both of the above effects are relatively small "constant" errors, which can be important
when calibrating at low pressures, but become less significant as the pressure increases.
SEPARATOR
RESERVOIR
DEAD WEIGHT
TESTER
PCU
Figure 1-1. Schematic of Separator/Deadweight Tester Arrangement
DEAD WEIGHT
TESTER
SCREW PUMP
Applying Pressure Corrections
DEVICE
UNDER
TEST
SEPARATOR
DEAD WEIGHT
TESTER
RESERVOIR
1
Preparation
gkq005.eps
1-3