‘Kepler, Sulphur Drawing’: The curved movement of a plotting electrode is recorded using the sulphur-marking system.

 

‘Kepler, Sulphur Drawing 1’: The curved movement of a plotting electrode is recorded using the sulphur-marking system. This produces time-interval marks. Using the distances between the marks as points of reference, one can measure the speed of the electrode. An alternating voltage at the mains frequency is applied between the electrode and the tracing plate, so that the sulphur powder is alternately attracted and repelled according to the changing polarity.

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