A guide: How to use the Tachymeter: A Guide to Measuring Speed with Your Watch

How do you use the Tachymeter on your watch?

A Guide to Measuring Speed with Your Watch

For watch enthusiasts and outdoor adventurers alike, the humble tachymeter can be an incredibly useful tool. This often-overlooked feature, found on the bezels of many chronograph watches, allows you to measure speed and rate over a fixed distance easily. Whether you're timing your morning run or calculating the pace of a passing vehicle, mastering the tachymeter can unlock a world of practical applications. Let's dive into how this ingenious complication works and how you can put it to use.

What is a Tachymeter?
A tachymeter is a scale on a watch's bezel (the ring surrounding the watch face) that is designed to measure speed or rate. The word "tachymeter" comes from the Greek words "tachys," meaning swift, and "metron," meaning measure. This scale typically displays numbers ranging from around 400 to 60, with smaller subdivisions in between.

How Does a Tachymeter Work?

Your main use of the tachymeter is to measure the speed of a vehicle over a known distance.
The tachymeter operates in conjunction with the watch's chronograph function, which measures elapsed time. To use the tachymeter, you'll need to know the distance over which you want to measure speed or rate. Here's how it works:

1. Start the chronograph at the beginning of the known distance.
2. Stop the chronograph when you reach the end of that distance.
3. Locate the elapsed time in seconds on the tachymeter scale.
4. The number on the tachymeter scale corresponding to the elapsed time indicates the speed or rate over the known distance.

For example, let's say you want to measure your running speed over a 1-kilometer (0.62-mile) distance. You start the chronograph at the beginning of the kilometer and stop it when you reach the end. If the elapsed time on the chronograph is 4 minutes and 20 seconds (260 seconds), you would look for the number 260 on the tachymeter scale. If your tachymeter scale shows "60" at the 260-second mark, it means you were running at a pace of 60 kilometers per hour (37.3 miles per hour) over that 1-kilometer distance.



Common Applications of the Tachymeter
While initially designed for timing automotive and industrial processes, the tachymeter has found various practical applications in modern times:

- Runners and cyclists can use it to measure their pace over a known distance.
- Outdoor enthusiasts can calculate the speed of a passing vehicle or object.
- Photographers can determine the appropriate shutter speed for capturing moving subjects.
- Pilots and navigators can measure ground speed during flight.



It's important to note that the tachymeter's accuracy depends on precisely measuring the known distance and starting/stopping the chronograph at the exact points. Additionally, some tachymeter scales are calibrated for specific units (e.g., miles or kilometers), so it's essential to understand the scale's markings on your particular watch.

While the tachymeter may seem like a niche complication, it can be an incredibly handy tool for those who take the time to understand and master its use. Next time you're out on a run or adventure, don't overlook the power of this unassuming little scale – it might just become your new favorite way to measure speed and rate with precision.