Pulsometer scale (chronograph pulse scale)
A pulsometer scale is fitted to some chronographs to convert a timed interval into beats per minute. It should be distinguished from a tachymeter scale used for speed. The scale provides the conversion, while the chronograph measures elapsed time.
Calibration states how many beats the timing is based on. The Longines L688 instructions describe a pulsometer scale based on 30 beats. With that calibration, 30 beats in 20 seconds corresponds to 90 beats per minute, calculated as 60 times 30 divided by 20. The figure 30 is not a universal specification for every pulsometer scale. Read the inscription on the particular dial and consult its matching instructions.
Longines also presented a Pulsometer Chronograph in 2015 drawing on an older design. Such a revival shows why appearance alone cannot date a watch. When assessing an older example, compare scale, lettering, dial finish, hands and reference with model documentation. Record any refinished or replacement dial and examine chronograph operation separately. The scale alone establishes neither original professional use nor previous ownership by a doctor.
