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The CNR 4 body and ambient air should be at the same temperature as much as possible. Let the pyrgeometer rest
for at least five minutes to regain its thermal equilibrium. Set the voltmeter to its most sensitive range. To test if the
pyrgeometer is working properly, we suggest putting your hand in front of the pyrgeometer. The thermal radiation
will cause pyrgeometer to generate a positive voltage when the hand's surface temperature is higher than the
pyrgeometer temperature. The pyrgeometer will generate a negative voltage if the hand is colder. The signal is
proportional to the temperature difference (see the rule of thumb of 1.1.6.5). 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 1.2. Still no faults found? Your pyrgeometer is probably doing fine.
5.3
Testing the Pt-100
Using a meter, which measures resistance, you can check the operation of the Pt-100. If connected properly, the
resistance of two opposite wires of the Pt-100 should be measured. The value can be read in the table 1.1 and
should be above 100 Ohms (cable resistance should measure about 0.1 ohms per metre cable). When in doubt the
thermistor resistance (temperature) can be checked as well for reference
5.4
Testing the thermistor
Using a meter, which measures resistance, you can check the operation of the thermistor. If connected properly, the
resistance of two wires of the thermistor should be measured. The value can be read in the table 1.2 and should be
around 10.000 Ohms for 25 °C. (cable resistance should measure about 0.1 ohms per metre cable). When in doubt
the Pt-100 resistance (temperature) can be checked as well for reference
5.5
Testing the Heater
The optional CNF 4 consists of a heater and ventilator. Using a meter, which measures resistance you can check the
operation of the heating resistor. The value should be around 15 Ohm. (Cable resistance should measure about 0.1
ohms per metre cable).
Using a meter, which measures resistance, you can check the operation of the heater. If connected properly, the
resistance of two opposite wires of the heater should measure about 8 ohms (this includes the cable resistance for
the standard 10-meter cable). The cable resistance should measure about 0.1 ohms per metre cable. An infinite
resistance reading indicates the likelihood of a broken wire, or cable.
5.6
Testing the Ventilator
The impedance of the ventilator motor can be checked to tested for reference The value should be around 30 Ohms
(cable resistance should measure about 0.1 ohms per metre cable). In this case a correct value is measured this
does not guarantee proper operation. It is possible the ventilator is stalled by an object blocking the fan. This can
be checked by removing the cover and filter and inspecting the rotation of the fan by hand.
