Campbell CNR1 Spécifications télécharger pdf (Page 26)

CNR1 Net Radiometer

Albedo=CM3Dn/CM3Up

UpTot=CM3Up+CG3Up

DnTot=CM3Dn+CG3Dn

NetTot=UpTot-DnTot

CG3UpCo=CG3Up+5.67*10^-8*CNR1TK^4

CG3DnCo=CG3Dn+5.67*10^-8*CNR1TK^4

'Call Data Tables and Store Data

CallTable(Table1)

NextScan

EndProg

7. Calibration

The CNR1 should be recalibrated every two years, or as an alternative, by

letting a higher standard run parallel to it over a two-day period and then

comparing the results. For comparison of pyranometers, one should use a clear

day. For comparison of pyrgeometers, one should compare nighttime results.

Deviations of more than 6% can be used to correct the calibration factors.

8. Troubleshooting

If there is no clue as to what may be the problem, start performing the

following "upside-down test", which is a rough test for a first diagnosis. It can

be performed both outdoors and indoors. Indoors, a lamp can be used as a

source for both Solar and Far Infrared radiation. Outdoors one should

preferably work with a solar elevation of more than 45 degrees (45 degrees

above horizon) and of course under stable conditions (no large changes in solar

irradiance, preferably cloudless).

1. Measure the radiation outputs in the normal position. Record the

measured values when the signals have stabilized, i.e. after about three

minutes.

2. Rotate the instrument 180 degrees, so that the upper and the lower sensors

are now in the reverse orientation as to the previous position.

3. Measure the radiation outputs once more. Record the measured values

when the radiometers have stabilized.

4. Since of the all sensors are trimmed, the values in the rotated position

should be equal in magnitude, only differing in sign. In a rough test like

this, deviations of +/- 10 % can be tolerated. If deviations greater than

this are encountered, the following tests might help.

8.1 Testing the CM3

As a first test we recommend that one check the sensor impedance. It should

have a nominal value as indicated in the specifications. Zero, or infinite

resistance, indicates a failure in hardware connection.

Before starting the second test measurement, let the CM3 rest for at least five

minutes to let it regain its thermal equilibrium. For testing, set a voltmeter to

its most sensitive range setting. Darken the sensor. The signal should read

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Campbell CNR1 Spécifications Page 26

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