Shortridge Instruments ADM-860C, Руководство по эксплуатации

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ADM-860C 04/14/08 34
7.0 PRESSURE MEASUREMENT
7.1 DIFFERENTIAL PRESSURE
Differential pressure measurements can be made with static pressure probes, a pitot tube or by connecting the
pneumatic tubing directly to any appropriate pressure source
within the safe operating limits for the meter .
The manner in which a pitot tube is connected to the meter is critical to the type of differential pressure
measurement obtained. The meter will display DIFF PRES and read out in the same units for all types of
differential pressure measurements.
The positive (+) and negative (-) ports of the meter are connected as a pair to the pneumatic pressure source
for differential pressure measurements. Maximum safe pressures for differential pressure measurements are
20 psid (900% full scale) and 60 psia common mode. The length of each external pneumatic tube should not
exceed 18 feet of 3/16" ID tubing.
Press the MODE key to toggle through the modes to differential pressure. The meter will display DIFF PRES
and then IN:READ. Press the READ key to obtain the pressure measurement.
The differential pressure between two rooms, or any other two areas may be obtained by connecting the tubing
to the positive (+) port of the meter and leaving the negative (-) port open to the ambient air pressure. Place
the end of the tubing in one area and place the meter in the other. The meter will measure the pressure
differential between the two areas.
7.1.1 STATIC PRESSURE PROBES
Static pressures are measured with static pressure probes. These probes are brass colored and have a single
tubing connection in the magnetic base. Connect the tubing from the static pressure probe to the positive (+)
port of the meter. Leave the negative (-) port open to the room air. Insert the static pressure probe into a 3/8"
hole drilled into the duct until the magnet is flush with the surface of the duct. Point the tip of the static pressure
probe directly into the airstream. Press the READ key. The meter will read the differential between the pressure
within the duct and the ambient pressure on the negative port of the meter.
7.1 STATIC PRESSURE PROBE
7.1.2 PITOT TUBE "VELOCITY PRESSURES"
Velocity pressures are obtained when a pitot tube is used and the meter is set to read out in differential
pressure. The resulting reading is recorded as velocity pressure. Connect one of the tubing sections from the
positive (+) port of the meter to the total pressure connection (in line with the main shaft) on the pitot tube.
Connect the other tubing section from the negative (-) port to the static pressure connection (perpendicular to
the main shaft). The pitot tube connections are shown in Figure 6.1. If the connections are reversed, the