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High-pressure Na lamps are widely used in office, shop and street lighting. However, they present a number of measurement problems which do not arise with incandescent lamps, due to the complex frequency-dependent temporal variations in light output and the intrinsic lack of stability in the discharge. In this intercomparison a set of five carefully manufactured 250 W high-pressure Na lamps were selected as transfer standards because of their stability, and circulated on a radial basis for measurements at fourteen different European laboratories. Five 95 V 1000 W tungsten filaments were also circulated in parallel, in order to distinguish the differences between the basic scales maintained by each laboratory and the measurement problems set by Na lamps. The measured mean luminous flux differences with respect to NPL ranged from +9.8% to -6.1%, the standard deviation being equal to 1.75%. This figure would drop to 0.64% if only eight laboratories were considered. Although, as expected, individual lamps showed fluctuations in output during use, these mean values proved to be more than adequate for the task of examining the ability of the participating laboratories to make photometric measurements on this type of Na lamp and suggested that such lamps might well be used, if required, to provide secondary standards.

Additional information

Authors: MOORE J R, National Physical Laboratory, Teddington (GB);GARFORTH F A, National Physical Laboratory, Teddington (GB);MOSS P G, National Physical Laboratory, Teddington (GB)
Bibliographic Reference: EUR 14076 EN (1992) 99 pp., FS, ECU 10.50
Availability: (2)
ISBN: ISBN 92-826-3668-2
Record Number: 199211104 / Last updated on: 1994-11-29
Original language: en
Available languages: en