Kipp & Zonen Brewer Mk III Operator's Manual page 17

Figure 2.4: Optical Elements of Brewer Spectrophotometer
Lamp Assembly
A quartz-halogen lamp [HL 1] provides a well-regulated light source which is used as a reference
for sensitivity measurements. The lamp is powered by a constant current source of nominal value
1.5 A, held to within 0.5% over a temperature range of -20° to +40° C. The intensity of the radiation
from the lamp under these conditions is stable to within 5%. The filament of the lamp is placed at
the focal point of a double-convex lens [LE 1] so that the light from the lamp is directed along the
optical axis by the zenith prism.
Beneath the halogen lamp is a mercury discharge lamp [ML 1], which provides a line source for
wavelength calibration. Ultraviolet radiation from the mercury lamp passes through the halogen
lamp to the zenith prism. While the actual light intensity of the lamp is not critical (a variation of
50% over the operational temperature range is normal), it must remain stable to within 5% for short
time periods (10 minutes).
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MKIII OPERATOR'S MANUAL