Campbell Scientific NR-LITE2 Net Radiometer - Manual (Page 27)

NR-LITE2 Net Radiometer
Conversely, if the sensor is warmer than your hand, the reading will
decrease.
8. 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.
9. 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 radiation +1500 W m -2
Min. radiation –200 W m -2
Sensitivity of the net radiometer 10 μV/(W m -2 )
Expected output range of the radiometer is (1500 + 200) Ч 10 =
1700 Ч 10 = 17.0 mV or 0.017 V.
9.2 Radiometer Produces No Apparent Output
If your net radiometer does not appear to be working at all, do the following
checks:
1. Check the instrument’s sensitivity to radiation, following the procedure
shown in Section 9.1, Checking Sensor Operation.
2. If this appears to produce no results, measure the impedance of the sensor
across the red and blue wires. The impedance reading should be close to
2.3
Ω. If it is virtually zero, a short circuit is indicated. If it is ‘infinite’,
the thermopile is blown.
9.3 Readings Are Not As Expected
1. Under full sunlight, the expected radiation value is about 1000 W m -2 .
Under lamps it may be greater. For indoor climate studies, smaller values
are to be expected unless solar radiation is present. A typical value for a
room when facing a wall and a relatively cold window is 50 W m
-2 .
2. Are you using the correct calibration factor? Note that this factor is unique
for each individual sensor as noted on the calibration certificate provided
with that sensor. Did you convert the factor to the correct value for the
datalogger program? (Section 7.2, Datalogger Programming.)
3. Check the datalogger program for errors.
If you cannot resolve your problems, please contact Campbell Scientific for
further advice.
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