Absolute Cavity Pyrgeometer (ACP)

Research output: NRELPresentation


ACP Measures atmospheric longwave irradiance with traceability to the International System of Units (SI). To date the Interim world reference World Infrared Standard Group (WISG) is traceable to blackbody (not sky/atmosphere), and InfraRed Integrating Sphere (IRIS) Developed by the World Radiation Center (PMOD) is traceable to blackbody irradiance. The ACP is self calibrated radiometer using heat substitution like Absolute Cavity Radiometer (ACR) that is self calibrated radiometer using electrical substitution to measure solar irradiance. ACP is a contribution to develop the world reference with traceability to SI, using the outdoor irradiance as the source, instead of blackbody.
Original languageAmerican English
Number of pages12
StatePublished - 2022

Publication series

NamePresented at the Japan Meteorological Authority (JMA), 8 May 2022, Tokyo, Japan

NREL Publication Number

  • NREL/PR-1900-82820


  • ACP
  • IRIS
  • pyrgeometer
  • SI
  • WISG


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