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Professor Elihu Thomson's Recording Wattmeter circa 1883

Supplying electricity was one problem charging for it by use was another. Edison's solution was to use a glass cell containing a solution of zinc sulphate with zinc plates and measure the increase in weight of the cathode which was proportional to the electricity usage. The defects in this system were obvious and additionally the customer had no way of knowing between the times the cathode was weighted how much electricity had been used. The world's first practical recording electricity meter was made by a German, Dr Aron. This was an electric "clock" meter with two clocks first proposed by Professors Ayrton and Parry in 1882 in which one of the clocks had a pendulum that was electro-magnetically controlled. Two clocks were mounted on the same base plate. The last wheels in the train of each clock were so geared together that if the clocks were going at the same rate the counting dials were not affected. If however one clock gained on the other, the dials registered the gain. If one clock was made to err at a rate proportional to the Watts, the total error was proportional to the watts consumed in a given time and thus the indicated the energy usage. Dr Aron's clock meter worked very well but in its early form it was a very expensive instrument really only suitable and economically practical for the generating stations in the main. It was neither a simple or an economic solution to the problem of mass home metering of electricity. The solution to this problem was devised by Professor Elihu Thomson. His electricity meter was in reality a small electric motor, so controlled that the speed of rotation of the armature is proportional to the power supplied, and therefor the total number of revolutions of the armature, which were automatically counted measured the total energy. Most electricity meters used this system for the next century. Professor Elihu Thomson's electricity meter offered here made by British Thomson Houston Co Ltd. London was manufactured in France. With its magnificent glass case it seems designed for collectors of early electric motors in the twenty-first century. In virtually mint condition this must be one of the most elegant electric motors ever produced. Case dimensions height 10.6" (27 cm) base front to back 8.5" (21.5 cm) width 8.9" (22.5 cm). Delivery at cost

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Elihu Thomson Electricity meter 1873
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Elihu Thompson Electricity Meter 1883
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Elihu Thomson Electricity Meter 1883 name plates
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Elihu Thomson Electricity Meter 1883
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Elihu Thomson Electricity Meter 1883
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Elihu Thomson Electricity meter 1883
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