50.5-9800 Rev C Page 5
Weather sensors are sensitive to direct or nearby lightning strikes. A well-grounded metal rod or
frame should be placed above the sensor installation. In addition, the shield on the signal cable
leading to the translator must be connected to a good earth ground at the translator end and the
cable route should not be vulnerable to lightning.
2.4 ORIENTATION WITH FIXTURE
The Orientation Fixture, Model 70.5, is used for very accurate positioning of the 50.5 sensor with
respect to a benchmark or other object that can be visually observed. If a compass is used to
establish a benchmark, the reading should be taken away from heavy metal objects, which can
affect the reading and should be corrected for declination of the magnetic north pole. The
benchmark is set to true north of the sensor site. Information on determining true North can be
found in Appendix A of this manual.
The fixture contains a telescopic sight with crosshairs and includes a keyed base identical to that
on the sensor. The fixture is specifically designed for use with the 3188 Sensor Mounting Fixture.
The base of the fixture is keyed so that the object lens of the sight assumes the same position as
the north side of the sensor.
Before orienting the sensor, ensure that it is vertical and adjust the cross arm as necessary.
Orientation of the sensor is then performed with the fixture installed on the cross arm in place of
the sensor. (The three screws in the base of the fixture must be tightened to ensure proper
orientation in the cross arm). Loosening the three setscrews on the side of the sensor mount
allows free rotation of the keyed bushing and orientation fixture. The ring and fixture are then
rotated to position the benchmark in the center of the sight crosshairs. The sight can be tilted as
necessary by loosening the slotted screw on the side of the fixture. The set screws are then
tightened, the fixture removed, and the sensor installed in its place. The sensor is now oriented
for zero (north) wind direction signal output when the wind is from north.
Figure 2-2
Orientation Fixture
The electrical connector on the bottom of the sensor should be properly mated to the cable
connector, and the three captive screws on the base of the sensor should be tightened.
When using the orientation fixture, assure that the two-piece mounting assembly is properly
aligned. The upper half of the assembly contains a horizontal peg, which must seat in the V-
notch located in the lower half. The knurled knob on the lower half is used to secure the two
sections and should be tight.
