Met One 50.5, Руководство по эксплуатации

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50.5-9800 Rev C Page 6
2.5. ORIENTATION WITHOUT FIXTURE (See FIGURE 2-3 and 2-4)
Establish a True North benchmark. See Appendix A for aids to determine True North. This should
be a point directly north from the sensor’s mounted location. This point should allow easy access
so that a person may sight the sensor with a spotting telescope. 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
due north of the sensor site.
One person is located at True North benchmark equipped with a spotting scope. A second
person is located at the sensor. The sensor alignment may be established as follows.
A. Install the sensor into the alignment bushing and secure with the two setscrews under the
3188 Alignment Fixture. Keep the three setscrews around the ring of the fixture loose so that
the ring can be rotated into position.
B. Turn the sensor so that the sensor points to the North benchmark. Tighten the 3 setscrews
and recheck alignment.
C. Connect the 3379-cable assembly to the sensor. Secure cable to boom with cable ties or
tape to prevent damage.
D. The sensor can be removed without requiring realignment at any time. Simply remove the
sensor. The alignment bushing remains properly oriented in the fitting.
2.6. EXTERNAL HEATER
The Optional External Heater provides de-icing for the sensor arms and prevents the
accumulation of ice, which might block the sonic sensor elements. The heater consists of a
laminated heater material that is custom designed and wrapped around the four sensor arms and
sonic sensor element housings. The heater controller requires 15 to 24 VAC/VDC at
approximately 4-5 amps at startup. There are jumper connections on the controller board for the
selection of power source. The controller is normally provided with the jumpers not installed.
This is for 24 volts AC operation of the heaters. Heater power can be supplied from a power
transformer or a Met One Instruments supplied power unit in a weatherproof box. The
proportional controlled heater uses maximum current at start-up and power requirement goes
down as the sensor/heater reaches stability. The heater is activated at 38 degrees F and will
keep the arms ice-free at temperatures down to below –20 degrees F. The connection
information can be found in Appendix C of this manual.
The temperature controller electronics box should be mounted no more than 5 feet from the
sensor using the cable supplied with the heater controller. The power cable should be of
minimum 16 AWG wire and cable length should be at a minimum to prevent power loss due to
cable resistance at the 4-amp power requirement.