Net Radiometers from Kipp & Zonen

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


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 has two pyranometers and two pyrgeometers. The pyranometers measure the short-wave radiation and the pyrgeometers long-wave. Positioned back to back, the four sensors measure both incoming and outgoing (reflected) solar insolation to provide the energy balance.

As an additional feature, the top long-wave detector of CNR4 has a meniscus dome. As a result, water droplets roll off easily and the field of view increases to nearly 180°, from 150° for a flat window.

Calibrated individually the pyranometers and pyrgeometers provide optimal accuracy. Also included in the CNR4 net radiation unit are two temperature sensors, a Pt-100 and Thermistor. The temperature sensor provides information to correct the infrared readings for the temperature of the instrument housing. Aiding compatibility with dataloggers.

The optional CNF4 ventilation unit with heater is designed to be an extension of the sun shield. Fit a CNF4 to a CNR4 when new, or retro-fitted. 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 melts frost.

The CNR4 and NR Lite2 both meet WMO standards.

Want to learn more about solar irradiance? Read our weekly articles.

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