D, AC version (1905 to 1907), E (1907) Previous
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After Sangamo was barred from making induction-type meters until Tesla's patents expired in 1910, they put a lot of effort in developing watthour meters using the mercury-motor principle (ampere-hour meters using this principle were very popular in England at the time).

Shortly after the Type D DC mercury-motor meter was introduced, Sangamo made an attempt to get back into the market for alternating-current meters by adapting this model for alternating current by adding a capacitor in series with the voltage coil. It worked but the accuracy varied widely with small variations of frequency and this verson was soon discontinued. In 1906, another attempt was made at an AC mercury-motor meter by using a small voltage transformer instead of the capacitor, and this version was a little more successful.

The Type E (shown) was a further refinement of the Type D (AC version) and quickly gave way to the new Type F meter.