CALIBRATION STANDARD
An array of tungsten strip lamps in
a spectral radiance measuring
set-up at a PTB lab in Berlin helps
metrologists establish a range of
high temperature reference points
needed for calibrating thermo-
meters and the dissemination of
the kelvin. With increasing tempe-
rature, color and intensity of the
radiation emitted by the glowing
filaments change: the hotter, the
whiter.