A Timegrapher is an instrument for the rapid determination of the current rate of a watch.
Modern timegraphers compare the oscillations of the balance wheel of a watch to be tested with those of an oscillating quartz crystal as a measure of time. Therefore the tick sound generated by the movement is recorded with a microphone and compared with the desired frequency. Since the accuracy of a mechanical watch is also dependent on the location, this is a quick way to determine a deviation. The time scale enables a quick evaluation of gait and position errors and many faults in the escapement. Therefore, a beat error, and with newer, electronic devices, the amplitude of the Balance wheel can be analyzed.
Former devices registered for each “tick” a short line on a continuous strip of paper. The slope of the formed lines then indicate the gait deviation of the watch, the distance of the lines is a reference to the beat error. Today's devices have an electronic display that digitally displays all relevant data.
A more time-consuming alternative to timegraphers would be to register the rate of the watch over a longer time period — several days as a rule. By comparing with a reference time, for example, with an atomic watch, a gaining or losing of time can be determined, which must be corrected in accordance with the escapement.
Reinhard Straumann built the first timegrapher together with Siemens, the so-called Chronokomparator.