Campbell Scientific CNR4 Net Radiometer - Manual (Page 38)

CNR4 Net Radiometer
'Convert CNR4 temperature to Kelvin
cnr4_T_K = cnr4_T_C+273.15
'Correct the long-wave radiation values from pyrgeometers
long_up_corr = long_up+5.67e-8*cnr4_T_K^4
long_dn_corr = long_dn+5.67e-8*cnr4_T_K^4
'Compute short-wave net radiation
Rs_net = short_up - short_dn
'Compute long-wave net radiation
Rl_net = long_up - long_dn
'Compute albedo
albedo = short_dn/short_up
'Compute net radiation
Rn = Rs_net + Rl_net
CallTable cnr4_dat
CallTable cnr4_ts
NextScan
EndProg
8. Tr
n as to what may be the problem, start performing the
st”, which is a rough test for a first diagnosis. It can
s and indoors. Indoors, a lamp can be used as a
wave and long-wave radiation. Outdoors, one should
th a solar elevation of more than 45 degrees (45 degrees
under stable conditions (no large changes in solar
rably no clouds).
e the radiation outputs in the normal position. Record the
d values when the signals have stabilized, i.e. after about three
he instrument 180 degrees, so that the upper and the lower sensors
are now in the reverse orientation as to the previous position.
puts once more. Record the measured values
have stabilized.
iation values in rotated position should be equal in
magnitude but only differing in sign. In a rough test like this, deviations
of ± 10 % can be tolerated. If deviations greater than this are encountered,
ting is warranted.
8.1
check the sensor impedance. It should have a nominal value as
ce, indicates a failure in
Before starting the second test measurement, let the pyranometer rest for at
least five minutes to let it regain its thermal equilibrium. For testing, set a
oubleshooting
If there is no indicatio
following “upside-down te
be performed both outdoor
source for both short-
preferably work wi
above horizon) and
irradiance, and prefe
1. Measur
measure
minutes.
2. Rotate t
3. Measure the radiation out
when the radiometers
4. The computed net rad
additional tes
Testing the Pyranometer
As a first test,
indicated in the specifications. Zero, or infinite resistan
hardware connection.
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