Campbell Scientific CNR1 Net Radiometer - Manual (Page 28)

CNR1 Net Radiometer
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8.2 Testing of the CG3
It is assumed that the amplifier circuit is the same as the one used for the CM3,
and that its zero offset is no more than a few watts per square meter, let us say
5 Watts per square meter just as an example (see second test in 7.1).
The pyrgeometer, the mounting plate, and ambient air should be at the same
temperature as much as possible. Let the CG3 rest for at least five minutes to
regain its thermal equilibrium. Set the voltmeter to its most sensitive range.
To test if the CG3 is working properly, we suggest putting your hand in front
of the CG3. The thermal radiation will cause CG3 to generate a positive
voltage when the hand's surface temperature is higher than the pyrgeometer
temperature. The CG3 will generate a negative voltage if the hand is colder.
The signal is proportional to the temperature difference (see the rule of thumb
of Section 4.5). The radiation that is emitted by the hand can be calculated by
dividing the pyrgeometer output by the calibration factor, and subsequently
correcting for the temperature, according to Equation 4.2. Still no faults
found? Your pyrgeometer is probably doing fine.
8.3 Testing the Pt-100
Using a meter which measures resistance, check the operation of the Pt-100. If
connected properly, the resistance of two opposite wires of the Pt-100 should
measure about 100 ohms (this includes the cable resistance for the standard 10-
meter cable). The cable resistance should measure about 0.1 ohms per meter
cable.