Shortridge Instruments ADM-860C, Руководство по эксплуатации

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ADM-860C 04/14/08 35
readings will be negative. Insert the pitot tube into a 3/8" hole drilled into the side of the duct, being careful to
align the point of the pitot tube so that it is facing directly into the airstream. If the negative (-) connection
(perpendicular to the main shaft) of the pitot tube is upstream and parallel to the duct, the point of the pitot tube
should be facing directly into the airstream.
7.1.3 PITOT TUBE "STATIC PRESSURES"
Static pressures may be obtained using the pitot tube and the differential pressure mode by connecting the
positive (+) port on the meter to the static pressure connection (perpendicular to the main shaft) of the pitot tube
and leaving the negative (-) port exposed to the ambient pressure. Insert the pitot tube into the airstream as
discussed under Section 7.1.2 PITOT TUBE “VELOCITY PRESSURES” above. The resulting pressure
differential is recorded as static pressure.
7.1.4 PITOT TUBE "TOTAL PRESSURES"
Total pressure measurements may be obtained using the pitot tube and the differential pressure mode by
connecting the positive (+) port on the meter to the total pressure connection (in line with the main shaft) of the
pitot tube and leaving the negative port of the meter exposed to the ambient pressure. Insert the pitot tube into
the airstream as discussed under Section 7.1.2 PITOT TUBE “VELOCITY PRESSURES” above. The resulting
differential pressure reading represents total pressure.
7.2 ABSOLUTE PRESSURE
The absolute pressure function is intended mainly to provide automatic air density correction for the velocity and
flow measurements. Absolute barometric pressure measurements are obtained when the negative (-) port is
open to the atmosphere and the meter is in the absolute pressure mode. The measurement range is 10-40 in
Hg.
Specific absolute pressure source measurements may be obtained by connecting the pressure source directly
to both the positive (+) and the negative (-) ports (
in common ) of the meter. Press the MODE key until ABS
PRES is displayed. The meter will then display Hg: READ (or Bar: READ). Press the READ key to take a
reading.
CAUTION
If an absolute pressure source is likely to be greater than 60 in Hg (30 psia ), the pressure
source must be connected in common to both the positive (+) and negative (-) meter ports
simultaneously . This precaution avoids excessive differential pressure input which will
damage the pressure transducer. Maximum safe pressure is 60 psia common mode and 20
psi differential pressure.
The absolute pressure measuring accuracy should be checked periodically. Readings taken with the negative
port (-) open to the atmosphere should be within ± 2% of the actual barometric pressure to assure rated
accuracy of density corrected flow and velocity readings.