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Enabling better global research outcomes in soil, plant & environmental monitoring.

Apogee SN-500 Net Radiometer

The new Apogee Instruments SN-500 four-component net radiometer features SDI-12 output.

  • Four-component Net Radiometer
    An upward-looking and downward-looking pyranometer, and an upward-looking and downward-looking pyrgeometer provide separate measurements of the four components of net radiation.
  • Onboard A/D Conversion and SDI-12 Output
    Apogee net radiometers feature onboard A/D conversion and SDI-12 output to eliminate the requirement of multiple analogue datalogger channels.
  • Individually Heated Radiometers
    Each radiometer includes an individual heater to increase accuracy by minimising the influence of dew, frost and snow on the filter.
  • Compact and Light Weight
    Designed to be light weight and small in size to facilitate easy mounting.
  • Cost-effective
    Apogee’s net radiometer is low cost compared to other four-component net radiometers on the market.

It can be connected to data loggers via SDI-12, ideal for use with the ICT SDI-12 Logger.

Shortwave (Pyranometers): 385nm to 2105nm (upward looking); 295 to 2685 nm (downward-looking); (50% points)
Longwave (Pyrgeometers): 5 to 30 μm (50% points)

The detectors have a linear response (less than 1% non-linearity) in the following ranges:
Net shortwave: 0 to 2000 W m-2
Net longwave: -200 to 200 W m-2

Input Voltage Range: 5 to 16 V DC (heaters are optimised to run at 12 V DC)
Current Draw (12 V DC Supply Voltage): Heaters on, communication enabled: 63 mA; Heaters off, communication enabled: 1.5 mA; Heaters off, communication disabled: 0.6 mA
Response Time (using SDI-12 Protocol): 1 s (SDI-12 data transfer rate; detector response time are 0.5 s)
Heaters (sensors individually heated): 62 mA current drain and 740 mW power requirement at 12 V DC
Operating Environment: -50 to 80°C; 0 to 100% relative humidity
Dimensions: 116 mm length, 45 mm width, 66 mm height
Mass: 320 g (with mounting rod and 5 m of lead wire)
Cable: M8 connector (IP67 rating) to interface to sensor housing; 5 m of four conductor, shielded, twisted-pair wire in a santoprene rubber jacket with pigtail lead wires

Pyrgeometer Specifications:

Sensitivity: 0.12 mV per W m-2 (variable from sensor to sensor, typical value listed)
Calibration Factor (Reciprocal of Sensitivity): 8.t W m-2 per mV
Calibration Uncertainty: ± 5%
Output Range: -24 to 24 mV
Measurement Repeatability: Less than 1%
Long-term Drift: Less than 2% change in sensitivity per year
Non-linearity: Less than 1%
Detector Response Time: 0.5 s
Field of View: 150°
Spectral Range: 5 to 30 µm (50% points)
Temperature Response: Less than 0.1 C-1
Window Heating Offset: Less than 10 W m-2
Zero Offset B: Less than 5 W m-2
Tilt Error: Less than 0.5%
Uncertainty in Daily Total: ± 5%
Temperature Sensor: 30 kΩ thermistor, ± 1°C tolerance at 25°C
Output from Thermistor: 0 to 2500 mV (typical, other voltages can be used)
Input Voltage Requirement for Thermistor: 2500 mV excitation (typical, other voltages can be used)

Pyranometer Specifications

Sensitivity: 0.057 mV per W m-2 (upward-looking); 0.15 mV per W m-2 (downward-looking); (variable from sensor to sensor, typical values listed)
Calibration Factor (Reciprocal of Sensitivity): 17.5 W m-2 per mV (upward-looking); 6.7 W m-2 per mV (downward-looking)
Calibration Uncertainty: ± 5%
Output Range: 0 to 114 mV (upward-looking; 0 to 300 mV (downward-looking)
Measurement Range: 0 to 2000 W m-2 (net shortwave irradiance)
Measurement Repeatability: Less than 1%
Long-term Drift: Less than 2% per year
Non-linearity: Less than 1%
Detector Response Time: 0.5 s
Field of View: 180° (upward-looking); 150° (downward-looking)
Spectral Range: 385 nm to 2105 nm (upward-looking); 295 nm to 2685 nm (downward-looking); (50% points)
Directional (Cosine) Response: Less than 20 W m-2 at 80° solar zenith
Temperature Response: Less than 0.1% C-1
Zero Offset A: Less than 5 W m-2; less than 10 W m-2 (heated)
Zero Offset B: Less than 5 W m-2
Uncertainty in Daily Total: Less than 5%

SN-500 Dimensions

Typical Applications

Net radiation is a key variable in the surface energy balance and influences turbulent fluxes, including evapotranspiration. Applications include measurements on flux towers and weather stations.

Net radiation is the sum of the four components shown below (incoming shortwave, outgoing shortwave, incoming longwave, outgoing longwave). Incoming shortwave incident on the surface is either reflected or absorbed by the surface material, and longwave radiation is emitted from the surface and emitted from the molecules of air in the atmosphere. Typical clear sky summer fluxes over grass and clear sky winter fluxes over snow are shown. A typical summer flux at solar noon would be +650 W/m2; in winter it would be 0 W/m2.

Net Radiation