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2.4.3 Barometric Pressure Sensor
The barometric pressure sensor is designed to be mounted indoors. This arrangement
assumes that the barometric pressure indoors and outdoors is equal. The barometric
pressure sensor is provided with a short cable that connects directly to the data
acquisition module.
Connect the barometric pressure sensor cable to the terminal strip on the data
acquisition module. This sensor has a three conductor cable. The RED wire is
connected to a +12V terminal. The BLACK wire is connected to a GROUND terminal
and the GREEN wire is connected to terminal A2.
The barometric pressure sensor is set for sea level when it leaves the factory and will
show absolute pressure readings at elevations below 1,200 feet. Because pressure
varies with elevation, the sensor must be adjusted to read correctly for the elevation at
which it is installed.
The barometric pressure range is 28.25 to 30.75 inches of mercury. Nominal barometric
pressure is 29.6 inches of mercury. If the reading is 28.25 or 30.75, the sensor must be
adjusted. This is done using the offset adjustment screw located on the side of the
sensor.
Before setting the barometric pressure offset for sea level, you must first obtain a
reliable barometric pressure for your location. This can be found by contacting the
nearest airport or weather service facility.
Call up the main menu (Figure 3, Page 9) on the display terminal by pressing "m" two
times. Press "2" for output format. Then press "1" for observation display (Figure 4,
Page 9).
While watching the display screen, slowly turn the offset adjustment screw. Turning
clockwise will decrease the pressure reading. You may have to turn the adjustment
screw 3 to 10 revolutions before the display starts to change. Turn the pot slowly in
single turn increments, then wait for the screen to update, every five seconds. If the
value is moving away from the correct value obtained above, turn the screw in the
opposite direction. Continue turning the screw until the displayed value agrees with the
value obtained from the airport or weather service.
2.4.4 Temperature and Relative Humidity Sensor
Connect the combination temperature and relative humidity sensor cable to the terminal
strip on the data acquisition module. This sensor has a five conductor cable. The RED
wire is connected to the +12 REF terminal. The BLACK wire is connected to a
GROUND terminal. The BROWN wire (humidity signal) is connected to the A4 terminal.
The WHITE (temperature signal) is connected to the A5 terminal and the GREEN wire
is connected to a GROUND terminal.
Summary of Contents for 110-WS-16
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