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Trilateral Intercomparison of Photometric Units Maintained at NIST (USA), NPL (UK), and PTB (Germany)



Yoshihiro Ohno, T Goodman, G Sauter


A trilateral intercomparison of photometric units between NIST (USA), NPL (UK), and PTB (Germany) has been conducted to update the knowledge of the relationship between the photometric units disseminated in the three countries. The luminous intensity unit (cd), the luminous flux unit (lm), and the luminous responsivity scale (A/lx) maintained at each laboratory were compared by circulating transfer standard lamps and photometers. The results showed that the relative luminous intensity values, with respect to the average, measured by NIST, NPL, and PTB were 1.0014, 1.0020, and 0.9965; the relative luminous flux values were 0.9995, 1.0033, and 0.9972; and the relative inverse values of the luminous responsivity (corresponding to illuminance) were 1.0020, 1.0008, and 0.9971, respectively. The results agreed within the stated uncertainties of the units maintained at the three laboratories.
Journal of Research (NIST JRES) -
104 No. 1


illuminance, intercomparison, luminous flux, luminous intensity, luminous responsivity, photometer, photometry, units


Ohno, Y. , Goodman, T. and Sauter, G. (1999), Trilateral Intercomparison of Photometric Units Maintained at NIST (USA), NPL (UK), and PTB (Germany), Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed March 1, 2024)
Created January 1, 1999, Updated February 17, 2017