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Absorption and reflection measurements in photometers are mostly performed at fixed wavelengths. For this purpose medium pressure mercury lamps offer several advantages. The spectrum shows narrow lines in the UV as well as in the visible range.
For quasi-monochromatic measurements the spectrum can be limited to one line with just a simple filter technique. Furthermore the single lines have a high irradi-
ance and high-resolution measurements can be performed with conventional techniques.
Heraeus St-series mercury lamps are stabilised medium pressure lamps especially developed for analytical applications. They are used in photometers, polarimeters, fluorimeters and other equipment. The emission lines have narrow bands, virtually monochromatic spectrum at constant, well reproducible wavelengths. Consequent-
ly, they are particularly suitable for absorption measurements. |
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St-series mercury lamps are stabilised by the geometry of the gas discharge, resulting in an accurate position of the arc. As a result, the noise is very low - in the order of 0.1%. The most favourable values of drift and noise are achieved when only the middle part of the light arc is used as the light source.
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The guaranteed operating life for all St-lamp types is 1000 hrs with a reduc-
tion of the output of max. 50%. The normal useful operating life can be be-
tween 2000 to 4000 hrs.
St-lamps should be mounted with the base down and an inclination from the vertical of less than ±20°. In DC operation, the lamp must be connected so that the anode is at the bottom.
MANUFACTURER SAFETY WARNING
UV radiation damages skin and eyes. Always wear protective glasses, gloves and clothing.
Right image: St 46 mercury lamp line spectrum |
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