Appendix B. CNF4 Heater/Ventilator
B-2
The heater power can be controlled using one of the SW12V channels of the
Campbell Scientific dataloggers. The heater’s current drain is approximately
850 mA at 12 Vdc (10 Watts). The ventilator draws additional 5 Watts of power
at 12 Vdc. Connect the power ground from the heater to a G terminal close to the
SW12V channel of the datalogger (i.e., not to an analogue ground near the
measurement inputs).
The heater power can be controlled by the datalogger program. 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.
Do not use the SW12 channel of a CR1000 or CR3000 to
simultaneously power the heater and ventilator.
Simultaneously powering the heater and ventilator will exceed
the current limit of the SW12 channel. If the heater and
ventilator need to be used at the same time, connect the
CNF4 to the 12V channel instead of the SW12 channel and
use an external relay to switch the power on and off. Refer to
Section 4.2 of the CR1000 and CR3000 manual for details on
the 12V current source limits.
B.2 Attaching the Optional CNF4 Heater/Ventilator Unit
to CNR4
1.
The CNF4 heater/ventilator unit comes with the following: the
heater/ventilator, the white solar shield, three pan-head screws with washers,
and four flat-head screws as shown in Figure B-1.
Figure B-1. CNF4 Package Contents
CAUTION
