hefner lamp การใช้

• Germany, Austria, and Scandinavia used the Hefnerkerze, a unit based on the output of a Hefner lamp.
• The Hefner lamp provided the German, Austrian, and Scandinavian standard for luminosity during the late nineteenth and early twentieth centuries.
• The Germans, however, dissented and decided to use a definition equal to 9 / 10 of the output of a Hefner lamp.