Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Intercomparison of the LBIR Absolute Cryogenic Radiometers to the NIST Optical Power Measurement Standard



Adriaan C. Carter, James A. Fedchak, Raju V. Datla


The Low Background Infrared (LBIR) facility at the National Institute of Standards and Technology (NIST) presently maintains four absolute cryogenic radiometers (ACRs) which serve as standard reference detectors for infrared calibrations performed by the facility. The primary standard for optical power measurements at NIST was the high accuracy cryogenic radiometer (HACR). Recently, an improved radiometer, the primary optical watt radiometer (POWR), has replaced the HACR as the primary standard. In this paper, we present the results of comparisons between the radiometric powers measured by the four ACRs maintained by the LBIR facility to that measured by the HACR and POWR. This is done by using a Si photodiode light-trapping detector as a secondary transfer standard to compare the primary national standards to the ACRs maintained by the LBIR facility. The technique used to compare an ACR to the trap detector is described in detail. The accuracy of the absolute optical power measurements is found to be within 0.1% of the primary standard for all the ACRs examined in this study.
Journal of Research (NIST JRES) -
111 No. 4


absolute cryogenic radiometer, ACR, calibration, electrical substitution radiometers, HACR, high accuracy cryogenic radiometer, intercomparison, LBIR, optical power measurement standard


Carter, A. , Fedchak, J. and Datla, R. (2006), Intercomparison of the LBIR Absolute Cryogenic Radiometers to the NIST Optical Power Measurement Standard, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed June 22, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 1, 2006, Updated February 17, 2017