Here - PMOD/WRC

if the measurement range of KRISS is wider than that of
TKK, the data measured beyond the measurement range of
TKK affect the ccf within a part in 10 6 . The difference of
the ccf for the illuminant A is 0.28 %, which exceeds the
standard uncertainty denoted in the parenthesis in Table 1.
The difference of the absolute responsivity at 555 nm
is -0.3 %. Considering the degree of equivalence of the
spectral responsivity between both institutes, -0.12 % at
550 nm [5], we can see that an additional difference,
-0.18 %, though much smaller than its standard uncertainty
of 0.40 %, has appeared in the responsivity comparison.
The aperture area measurements are compared using
four apertures with diameters of 5 mm, 7 mm and 8 mm.
For all apertures, the relative area difference of KRISS and
TKK is between -0.005 % and -0.048 %. The area
measured by TKK and its difference with KRISS shown in
Table 1 is estimated from the area comparison result for
the aperture which has the same diameter as the aperture
attached in the artifact photometer.
The final difference of the illuminance responsivity of
the artifact is -0.6 %, which mainly comes from
contributions of difference of the responsivity at 555 nm
and of the ccf for the illuminant A. The aperture area
difference is somewhat larger than the standard uncertainty,
but its contribution to the illuminance responsivity
difference is almost negligible.
Table 1. Comparison of quantities obtained during realization of
the illuminance responsivity for the artifact. The numbers in the
parentheses correspond to the standard uncertainty.
Quantities KRISS TKK
Responsivity at
555 nm (A/W)
Aperture
(cm 2 )
area
ccf for
illuminant A
Illuminance
responsivity
(nA/lx)
KRISS-TKK
0.1974(6) 0.1980(4) -0.3(4) %
0.38492(6) 0.38507(10) -0.04(3) %
0.9958(14) 0.9930(12) 0.28(19) %
11.17(4) 11.24(3) -0.6(4) %
III. Comparison of illuminance responsivity
At TKK, the illuminance scale is not realized by using
the above procedure, but by using trap-detector based
photometers, for which the V(λ) filter is separately
measured in terms of spectral transmittance.[3] The
spectral responsivity of the trap detector is also calibrated
traceable to the cryogenic radiometer. The radiometric
aperture area is measured by GBS.[2]
The TKK reference photometer was compared with the
artifact photometer at TKK. The artifact drift during the
comparison period and transportation was checked after
return to KRISS and revealed to be insignificant. The
difference in the illuminance scales was -0.1 %, with an
expanded uncertainty of 0.9 %, which is much smaller
than the difference of -0.6 % shown in Table 1. However,
the differences are within combined standard uncertainties
of the comparisons. In another illuminance responsivity
comparison the difference between KRISS and TKK was
-0.2 % with an expanded uncertainty of 0.6 % [6].
Considering these facts, the deviation of -0.6 % of Table 1
is acceptable. However, both institutes seem to be
somewhat too optimistic with the uncertainty estimates.
IV. Conclusions
The illuminance scales realized and maintained at
KRISS and TKK have been compared to show a good
agreement between 0.1 and 0.2 %. TKK was asked to yield
the illuminance responsivity of the artifact photometer
supplied by KRISS according to the KRISS procedure.
The illuminance responsivity given by TKK using the
KRISS procedure is 0.6 % higher than that given by
KRISS. Considering the uncertainties of the measurements,
the difference is acceptable. However, since both institutes
seem to be somewhat too optimistic with the uncertainties
of the ccf and the aperture area, the uncertainties may need
to be addressed to cover these deviations.
References
[1] Khler R., Stock M. and Garreau C., Final Report on
the International Comparison of Luminous Responsivity
CCPR-K3.b, Metrologia 41, Tech. Suppl., 02001, 2004.
[2] Ikonen E., Toivanen P. and Lassila A., A new optical
method for high-accuracy determination of aperture area,
Metrologia 35, 369, 1998.
[3] Kh P., Haapalinna A., Toivanen P., Manoochehri F.
and Ikonen E., Filter radiometry based on direct
utilization of trap detectors, Metrologia 35, 255, 1998.
[4] Manoochehri F., Kärhä P., Palva L., Toivanen P.,
Haapalinna A., and Ikonen E., Characterization of
Optical Detectors Using High-Accuracy Instruments,
Anal. Chim. Acta 380, 327 (1999).
[5] Goebel R. and Stock M., Report on the comparison
CCPR-K2.b of spectral responsivity measurements in
the range 300 nm to 1000 nm, Metrologi, 41, Tech.
Suppl.,02004, 2004.
[6] Ikonen E. and Hovila J., Final Report of
CCPR-K3.b.2-2004: Bilateral Comparison of
Illuminance Responsivity Scales between the KRISS
(Korea) and the HUT (Finland), Metrologia 41, Tech.
Suppl. 02003, 2004.
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