Estimated Date: 1930
Manufacturer: Cambridge Instrument Company
Description: Wooden case contains a string galvanometer with magnets in housing, knob to adjust string. The case is 19” long, 10.5” high and 8” deep. With the top closed the height adds 4”. Light shines through housing to enter a box containing light sensitive paper. A mirror reflects a scale into the box as well and paper advances into a drum, which can be closed and removed. There is a counter. The lowest patent number is 1702650, which corresponds to a date between 1929 and 1930. There is a gear mechanism to advance the photographic paper and a counter and a timer wheel. Some of the original wiring is in the compartments. Extra compartments in the lid of the box are empty but held electrodes and wiring and extra materials. There is an on-off switch in the front of the device.Jump The Dutch physician Willem Einthoven (1860-1927) invented the electrocardiogram (ECG) in 1903 and received the Nobel Prize for the invention in 1924. The abbreviation EKG refers to the German spelling of the name. His device was the string galvanometer that detected the small amounts of current arising from contraction of the heart. The string galvanometer was replaced by the vacuum tube amplifier in the late 1930’s. We now use transistors and solid state circuitry.
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