| Jaquet Graphic Chronometer | |
| Written by AnubisTTP on 2025-01-10 |
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A graphic chronometer is an obscure type of specialized timer designed to be used as a timebase for physiographs and other pieces of laboratory equipment. The example shown here, produced by James Jaquet S. A. sometime in the early 20th century, is built around a square metal mechanical timer with an articulated scribe that that can be set to pulse at regular intervals. This timer would normally be paired with a physiograph, a sort of early mechanical chart recorder which uses a metal drum covered in oil lamp soot to record a signal or measurement over time. Mechanical or pneumatic arms would be connected from the physiograph to the object to be measured, which would scratch lines or marks into the soot-covered drum as it rotated in the mechanism. In operation the scribe of the graphic chronometer would be brought into contact with the soot-covered drum, where it would make marks in the soot at regular intervals to provide a timebase for observations. A small lever on the front of the device allows the scribe to be set for 6, 3, 1, or 1/2 second pulse intervals. This graphic chronometer also includes two dials that allow it to function as a stopwatch, showing elapsed minutes and seconds since the device was reset. A pair of screw contacts provide access to a switch closure that is attached to the scribe arm, which allows this device to be used as an electrical timebase as well as a mechanical one.
Jaquet S. A. produced several different versions of this timer, some of which omitted the two dials and stopwatch functions. Other variations had scribe intervals of up to 60 seconds, or scribes that could produce marks of different length based on the time interval. The example shown here appears to be one of the more common variants.
Jaquet graphic chronometer, at rest. This device was designed to be used as a timebase for physiograph instruments.
In use, the graphic chronometer would be mounted to a laboratory ring stand with the scribe touching the drum of the physiograph.
Winding of the movement is accomplished with a metal knob on the back of the device.
Jaquet produced graphic chronometers in variants both with and without dials.
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