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F.4
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FIELD OPERATION
In field use, the gage is placed in a louvered box which serves
to minimize wind effects. The spring drive motor is wound and started
approximately six hours before the desired recording time. During
this period, the pressure relief screw is open permitting pressure
equalization.
This permits the base line scratched on the disc to be
a true representation of the ambient pressure.
Just prior to the
expected phenomena, the pressure relief screw is closed making the gage
completely pressure tight.
At some time prior to or foilowing the recording of the pressure
phenomena, time pips are placed on the record disc. This is acconi plished by removing the relief screw and inserting a small rubber tube.
Aivery slight suction is applied by mouth deflecting the diaphragm and
“producing a sharp pip on the record disc.
<A number of pips are record-
ed, in ‘this manner at accurately known time intervals.
F.5 :PRESENTATION OF DATA
The datairecorded by the VLP gages are presented in two forms.
One form is/the actual enlarged photograph and the other form is a
linearized ‘curve of pressure versus time,
These are presented to show
the correlation between this method of measurements and those made by
Sandia Corporation-ging microbarographs (see Figures F.1, F.2, F.3,
F.4). Four representative records were chosen for this comparison.
:
F.6
5
DISCUSSION AND’,RECOMMENDATIONS
The comparison ofa records made by BRL and SC at the same
locations show excell
rrelation. The only difference being on
Site Elmer on Shot 1
ot the record from the BRL gage shows evidence
of a leak as it does not recgep all of the pressure flux indicated by
the SC record.
Ini addition to being sii e to operate, and constructed of few
parts the gage records directly on the recording disc and does not re-
quire the additional calibration ofsmplifierg and recording equipment.
The amplification of the record is!‘obtained through the optic system
of a toolmaker's microscope.
i ro
The gages were usually plecedjdin the field six to eight hours
before shot time and could be left “inattended, if necessary.
For an
inexpensive, self-recording, sensitive pidssure time gage the VIP gage
hes proven itself to be reliable and accurate.
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