CNR4 Net Radiometer

  • Light Weight
  • ISO 9060 Spectrally Flat Class C Pyranometers
  • Optional integrated ventilation unit

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CNR4 Net Radiometer

The CNR4 net radiometer measures the energy balance between incoming short-wave and long-wave Far Infrared (FIR) radiation versus surface-reflected short-wave and outgoing long-wave radiation. 

The CNR4 net radiometer consists of a pyranometer pair, one facing upward, the other facing downward, and a pyrgeometer pair in a similar configuration. The pyranometer pair measures the short-wave radiation. And the pyrgeometer pair measures long-wave radiation. The upper long-wave detector of CNR4 has a meniscus dome. This ensures that water droplets role off easily and improves the field of view to nearly 180°, compared with a 150° for a flat window. All 4 sensors are integrated directly into the  instrument body, instead of separate modules mounted onto the housing. But are each calibrated individually for optimal accuracy.

Two temperature sensors, a Pt-100 and Thermistor, are integrated for compatibility with every data logger. The temperature sensor is used to provide information to correct the infrared readings for the temperature of the instrument housing. Care has been taken to place the long-wave sensors close to each other and close to the temperature sensors. This assures that the temperatures of the measurement surfaces are the same and accurately known. Which improves the quality of the long-wave measurements.

The design is very light in weight and has an integrated sun shield that reduces thermal effects on both long-wave and short-wave measurements. The cables are yellow with waterproof connectors as used with all our new radiometers. The mounting rod can be unscrewed for transport.

An optional CNF4 ventilation unit with heater is designed as an extension of the sunshield and can be fitted new to the CNR4 or retro-fitted later. This unit is compact and provides efficient air-flow over the domes and windows to minimize the formation of dew and reduce the frequency of cleaning. The integrated heater can be used to melt frost.



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Spectral range (50% points) 0.3 to 2.8 µm = 300 to 2800 (short wave) nm
Spectral range (50% points) 4.5 to 42 µm = 4500 to 42000 (long wave) nm
Sensitivity 5 to 20 µV/W/m²
Temperature dependence of sensitivity (-10 ºC to +40 ºC) < 4 %
Response time < 18 s
Non-linearity < 1 %
Operating temperature -40 to +80 °C for CNR4, -40 to +70 °C for CNF4 °C
Power supply 12 VDC, 1.25 A (with heater on) for the optional CNF4 ventilation unit
Ventilation power 5 W continuously
Heating power 10 W externally switched



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