6-1
Chapter 6
Pressure Corrections
Introduction
Pressure correction is required for high accuracy work and is due to the effects of
pressure on the PCU assembly during operation. By reference to the certificate of
calibration provided the actual pressure in the system can be obtained. All values relate to
the environmental conditions stated on the certificate.
The pressure in the system when the carrier is loaded with major weights can be read
directly from the second column of the certificate.
The pressure in the system when the carrier is loaded with incremental weights is given
together with the pressure in the system when the carrier is loaded with major and
incremental weights. From these values, assuming effects are linear, the incremental
weight corrections over the range may be calculated.
If the DWT is located at a position where the values of the gravitational acceleration and
temperature of the operation are the same as those values specified for calibration, then
the Actual Pressure is fully corrected. If the DWT is used under different conditions then
further correction is necessary. The reference level is specified on the certificate.
Incremental weight
pressure correction
CORRECTED
PRESSURE
P1
ACTUAL
PRESSURE
P2
INDICATED
PRESSURE
(ON WEIGHTS)
Add indicated
carrier pressure
Apply temperature
and gravitational correction
glf11.eps
Figure 6-1. Pressure Corrections
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