Campbell CMP11-L, Инструкция по эксплуатации

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Appendix A. CVF3 Heater/Ventilator
A.1 General Information
The CVF3 consists of a ventilation unit and heaters. The ventilation unit uses a
fan and inlet filter to draw clean air over the pyranometer’s domes. The fan
runs continuously to reduce dust and dirt settling, to dissipate rain drops, and to
stabilize the dome temperature.
The CVF3 has both a 5 W and a 10 W heater. The 5 W heater raises the
temperature of the dome slightly above ambient temperature to prevent the
formation of dew and frost. The 10 W heater is used for more extreme
climates to melt snow and ice.
The 10 W heater’s current drain is approximately 850 mA at 12 Vdc, and the
5 W heater’s current drain is approximately 420 mA at 12 Vdc. The ventilator
draws an additional 5 W of power at 12 Vdc. These power requirements are
large compared to most Campbell Scientific products. Because of this, the
CVF3 should be connected to the 21326 Power Net 5 A Power Supply and the
7321 Crydom Relay.
The Crydom relay allows the heater power to be controlled by the datalogger
program and thus reducing power consumption. For example, the datalogger
program can turn on the heater only when the light level falls below 20 W/m
2
or, if a measurement of air humidity is available, when the dew point of the air
falls to within 1ºC of the sensor body temperature.
A.2 Siting
Siting information provided in Section 4.1, Siting , is pertinent when using the
CVF3 heater/ventilation. Additionally, the area directly under the CVF3’s
120-mm diameter hole needs to be free from snow, leaves, or other
obstructions that could inhibit the air flow (see FIGURE A-1).
FIGURE A-1. Transparent view of CVF3 shows air flow
A-1