Campbell NR-Lite, Instruction Manual, Page: 19 / 20

NR-LITE Net Radiometer
13
introduce thermal shocks. Hold the instrument only by its mounting arm at all
times.
Follow the procedure outlined below:
•
Connect the NR-LITE wires to the voltmeter. Connect the white wire to
the positive lead and the green wire to the negative lead.
•
Select the most sensitive range on the voltmeter.
•
With the lamp switched off, read the sensor output signal – allow a minute
or so for the signal to fully stabilize.
•
Switch on the lamp. The sensor should now producer a higher positive
reading.
•
Turn the lamp off again, when the signal should slowly return to its
original level, proving the sensor’s sensitivity to light.
•
Turn the sensor upside down. The signal value should reverse in sign (i.e.
a +10 mV signal should become a –10 mV signal). Don’t worry if the two
values are not exactly the same (up to 10% difference) as the sensor
profiles can vary. After completing this test, return the sensor to its
original orientation and let it stabilize.
•
Put your hand over the upper sensor. Assuming that your hand is at a
higher temperature than the sensor the positive reading should increase.
Conversely, if the sensor is warmer than your hand the reading will
decrease.
•
Check the radiometer’s sensitivity to thermal shocks by touching the edge
of the sensor (the blank metal) with your hand for some seconds. The
resultant shock will result in a signal drift, or a zero offset that will take
some time to settle back to zero.
•
Adjust the range of the voltmeter so that the expected full-scale output of
the radiometer is about the same as the range of the voltmeter. A
(theoretical ) way to calculate the maximum expected output for normal
meteorological applications is shown below:
Max. expected rad1500 W m
-2
Min. radiation –200 W m
-2
Sensitivity of the net radiometer 10
µ
V/(W m
-2
)
Expected output range of the radiometer is (1500+200) x 10 =
1700 x 10 = 17.0 mV or 0.017 V.
7.2 Radiometer produces no apparent output
If your net radiometer does not appear to be working at all, do the following
checks:
•
Check the instrument’s sensitivity to radiation, following the procedure
shown in Section 7.1.