Absolute Cavity Pyrgeometer (ACP)

Research output: NRELPresentation


Measure atmospheric longwave irradiance. ABSOLUTE measurement traceable to International System of Units (SI). To date, Interim world reference traceable to blackbody (not sky/atmosphere), World Infrared Standard Group (WISG). InfraRed Integrating Sphere (IRIS) Developed by the World Radiation Center (PMOD) is traceable to blackbody irradiance. 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 pages11
StatePublished - 2022

Publication series

NamePresented at the Metrology for Climate Action 2022 Workshop, 24-26 September 2022

NREL Publication Number

  • NREL/PR-1900-83907


  • ACP
  • IRIS
  • pyrgeometer


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