Dr. Jaques Arsène d’Arsonval’s chronometer
The 1890 published catalogue „Catalogue des Instruments de Précision pour la Physiologie et la Médecine construits par Charles Verdin” listed within the section of “Medical Instruments” contains a chronometer designed by the physicist and physician Jacques-Arsène d'Arsonval (1851-1940). Originally invented to measure the speed of the sensations of the nerves, the chronometer enabled D’Arsonval to differentiate between nerve diseases and hysteric phenomena.
Due to its unique clockwork, the chronometer is able to reach one rotation per second. Since the scale of the clockwork is divided into one hundred equidistant stages, times in the range of hundredths of seconds can be registered. In addition to that, the clockwork can be ran at different speed levels, providing a resolution within milliseconds.
The mechanics of d’Arsonal’s chronometer can be compared to Hipp’s chronoscope. By activating the electromagnet, the running mechanic clockwork decouples the watch hands. As soon as the current flow is cut off, the watch hands start turning until the current is turned on again.