An AC/DC Technique for the Absolute Integrating-Sphere Method
Yoshihiro Ohno, R Kohler, M F. Stock
The Bureau International des Poids et Mesures (BIPM) has historically maintained the results of international intercomparisons of luminous intensity and luminous flux as so-called world-mean values in the form of groups of lamps for more than 60 years. It was recently decided that this is no longer a satisfactory and reliable means of maintaining the photometric SI units at the BIPM. To maintain the luminous flux unit, an attempt was made at the BIPM to use the Absolute Integrating Sphere method developed at the National Institute of Standards and Technology (NIST). A new technique (AC/DC Technique) employing a chopper for the external source, which allows for measurement of the internal source and the external source simultaneously, has been developed to overcome an unexpected problem with the BIPM sphere characteristics. This method allows for absolute calibration of the integrating sphere while the internal lamp is operating and being measured. The experiments at BIPM revealed a problem of the effect of heat from the lamp on the sphere coating. After implementing this technique and replacing the sphere coating, experiment on the derivation of the unit is in progress. The preliminary results of the experiments using this technique at BIPM and NIST are reported.
coating, heat, integrating sphere, intercomparison, lumen, luminous flux, self-absorption, unit
, Kohler, R.
and Stock, M.
An AC/DC Technique for the Absolute Integrating-Sphere Method, Metrologia
(Accessed June 1, 2023)