Round Type (1897 to 1903) Previous
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The Shallenberger 'integrating wattmeter' met the industry need for a watthour meter, but it was too heavy and expensive. Since O.B. Shallenberger was too ill at the time to do any further work, two other engineers (H. P. Davis and Frank Conrad) were selected to design a lightweight and cheap watthour meter, and their result was known as the 'Round Type' or Davis & Conrad meter. This meter was much lighter at only 12 pounds, and introduced several features that are still in use today on modern meters: lightweight disk, small air gaps, power factor adjustment, and separate covers for the movement and terminals. This meter is quite distinctive with its 5-dial watthour register and terminal chamber located on the back of this meter. The light load adjustment on this model was unique as it involved varying the voltage supplied to the voltage coils. The Round Type meter was the last model made by Westinghouse to use a pivot-type bearing. There are 2 types of nameplates known on the glass-covered Round Type meters - a large porcelain-faced plate and a smaller brass plate.
 
Round Type, metal cover
Electrical Meterman's Handbook
Round Type, glass cover
Northeast Utilities collection
Rear view
Photo by Glenn Grabinsky