Posted in | Pyrgeometers

4 - Component Net Radiometer NR01

The NR01 is a market-leading 4-component net radiometer primarily utilized in scientific-grade energy balance and surface flux research. It provides four different measurements of global and reflected solar radiation, as well as downwelling and upwelling longwave radiation, with two sensors pointing up and two facing down.

NR01 has gained worldwide popularity due to its exceptional price-to-performance ratio and significant enhancements compared to similar instruments. Its advantages include a modular design featuring 2 pairs of identical sensors, lightweight construction, easy levelling, and minimal solar offsets in longwave measurement. Moreover, its unique ability to heat the pyrgeometers reduces measurement errors caused by dew deposition, making it stand out from its counterparts.

Net Radiometer 4-component NR01

Image Credit: Hukseflux Thermal Sensors B.V.


Source: Hukseflux Thermal Sensors B.V.

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Measurand downward longwave radiation*, global solar radiation, net radiation, reflected solar radiation, upward longwave radiation*
Optional measurand albedo or solar reflectance, sky temperature*, solar duration, surface temperature*
Included sensors 2 x identical ISO 9060 spectrally flat Class C pyranometers 2 x identical pyrgeometers with 150° field of view angle
Spectral range solar 285 to 3000 x 10⁻⁹ m
Calibration traceability solar to WRR
Calibration uncertainty solar < 2.4 %
Spectral range longwave 4.5 to 42 x 10⁻⁶ m
Calibration traceability longwave to WISG
Calibration uncertainty longwave < 7 %
Temperature sensor Pt100
Heater on pyrgeometer 1.5 W at 12 VDC
Rated operating temperature range -40 to 80 °C
Required readout 4 x DC voltage, 1 x Pt100
Levelling 2-axis leveling assembly (included)
Mounting on a 1 inch NPS tube; NR01 delivery includes a shim for alternative mounting on a ¾ inch NPS tube (tubes not included)
Standard cable length 2 x 5 m (see options)
* Required measurand instrument body temperature



  • 10 kΩ thermistor instead of Pt100 temperature sensor
  • Longer cable, in multiples of 5 m, and cables longer than 20 m, in multiples of 10 m


NR01 Measures the 4 Separate Components of the Surface Radiation Balance

NR01 measures 4 components of surface radiation balance: downward and upward solar radiation, as well as downward and upward longwave radiation. Solar radiation is captured using pyranometers, and longwave radiation is measured with pyrgeometers. These measurements help calculate net radiation.

Hukseflux 4 - Component Net Radiometer

Image Credit: Hukseflux Thermal Sensors B.V.

To accurately determine sky and surface temperatures, this net radiometer compensates for heat emitted by the pyrgeometers using the Stefan-Boltzmann law, assisted by an integrated Pt100 temperature sensor. Sunshine duration can be estimated using the WMO-approved pyranometric method.

NR01 Net Radiometer Operation

Hukseflux 4 - Component Net Radiometer

Image Credit: Hukseflux Thermal Sensors B.V.

The NR01 net radiometer is very easy to use. It can be directly connected to widely used data logging systems. Irradiance levels in W/m² are determined by dividing the NR01 outputs (small voltages) by the provided sensitivities. To ensure accuracy, the longwave irradiance should be adjusted based on the instrument's body temperature. All sensor sensitivities are specified on the NR01's product certificate.

Benefits of the NR01 Net Radiometer

The NR01 net radiometer prevents water condensation on its pyrgeometer windows by using internal heating near the sensors, ensuring it stays above the dew point. This feature is crucial, especially at night when condensation risk is high and water can block longwave radiation. This design significantly enhances the reliability of longwave radiation measurements. The instrument also has minimal solar offsets in longwave radiation measurements.

Hukseflux 4 - Component Net Radiometer

Image Credit: Hukseflux Thermal Sensors B.V.

The NR01 net radiometer has a modular design with two pairs of identical sensors: it is possible to take the instrument apart and easily replace individual sensors and recalibrate them using the same procedure. Features like these have made NR01 net radiometers popular in energy balance and surface flux studies.

In addition, this net radiometer is easy to mount; it is much lighter than competing models, and a 2-axis levelling assembly is included. The levelling assembly fits a 1-inch NPS tube (the tube’s recommended outer diameter equals 33.4 x 10⁻³ m). The NR01 shim, provided with the NR01, allows the use of a ¾ inch NPS tube.


Suggested Use

  • Climatological networks
  • Energy balance studies
  • Surface flux measurements

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