The right bezel can greatly enhance a watch’s functionality; the challenge lies in narrowing down the available options. Should it rotate? If it should, in one or both directions? What type of markings should it have?
Rotating bezels tend to come in two variations. A diver’s rotating bezel only turns counter-clockwise, and comes with count up markings to allow its user to measure elapsed time by aligning the marker at 12 o’clock with the minute hand. Other timepieces, such as pilot’s watches, tend to have bi-directional rotating bezels containing either count up markings that function similarly, or count down markings that function as reminders for time sensitive events.
The alternative to these are bezels with specific markings that must be used together with the chronograph seconds hand. These are usually fixed bezels, although manufactures including TAG Heuer have made rotating ones in the past.
The most common one is the tachymeter, which allows the wearer to read off its markings for the hourly rate of an activity, by measuring the time it takes to complete one unit of it. Starting the chronograph and stopping it after a car has travelled for one kilometre, for instance, will give the car’s speed in kilometres per hour – the wearer just needs to see where the chronograph seconds hand is pointing to on the tachymeter. The unit does not matter; one can arrive at the number of cookies a person eats in an hour by measuring the time he takes to finish one cookie.
The pulsometer and telemeter function similarly to the tachymeter, but are more specialised. A pulsometer gives the heart rate of a person (in beats per minute) by using the chronograph to measure the time it takes for a certain number of heart beats, usually 10 or 30. The telemeter, on the other hand, indicates the distance to an event, such as a lightning strike. The chronograph is started when the event is seen, and stopped when it is heard. By assuming that light travels instantly, while sound’s average speed through air is around 300m per second, a calibrated scale – the telemeter – can be made, and the distance to the event read off it.
|| THE VERDICT ||
The tachymeter is an easy pick here for being the “Goldilocks” bezel – it is neither too general to make proper use of the chronograph, like the diver’s bezel, nor too specialised, like the pulsometer. The flexibility inherent to the tachymeter is also an important advantage – any event can be timed and instantly converted to give an hourly rate.
Longines Pulsometer Chronograph
Tudor Fastrider Black Shield with tachymeter on bezel