Easy Watch Tachymeter Guide to Measure Speed and Distance

Sports watches often offer a range of features that can be very useful and allow for accurate timekeeping during training. In addition to the popular chronograph (stopwatch), there is another interesting feature. A tachymeter that measures speed. A watch tachymeter is explained below.

A tachymeter is a scale, usually based on the bezel of a watch, which can measure the average speed. It connects with the chronograph in order to work precisely.

The most common use of a tachymeter is to measure the approximate speed of a vehicle over a known distance.

For example, based on how many seconds it takes a car to travel 1km or 1 mile (measurable range is up to 60 seconds), you can calculate the average speed within a distance.

How to use watch tachymeter?

  • Start the chronograph when the vehicle starts moving.
  • Stop the chronograph after the vehicle has traveled 1 km or 1 mile.

The approximate average speed within the range can be determined by observing the current position of the second hand and reading the outer bezel.

Note: The tachymeter reading may appear on the dial ring instead of the outer bezel (depending on model).

Which watches have a tachymeter function?

Tachymeter scales are mostly found on sports watches and have a typical dial and bezel design. The most sporty model with a tachymeter is the Emporio Armani watch, a watch from the Japanese brand Lorus (sports series) with a stainless steel bracelet.

Sometimes elegant watches with steel or leather straps are equipped with tachymeter scales. Among them, I would like to pay attention to the Casio Edifice watch that surrounds the tachymeter function with an elegant design. This scale can also be seen in the stylish Zeppelin 100 Years watch, a vintage model considered a timeless watch.

How can we measure speed using watch tachymeter?

To measure speed with a tachymeter, you need to know the distance travelled.

Imagine you’re in a car on the highway and the speedometer isn’t working but the highway patrol is alert and you don’t want to get a speeding ticket.

Watch out for the mile markers and press the chronograph start button as soon as you pass them.

Tachymeter Start Milestone

After passing the next mile marker, press the stop button and note the number, the timer hands are pointing to.

Tachymeter stop milestone

When the car covers the 1-mile, measure where the second hand points on the tachymeter scale. In the above example, when the one mile is complete, the second hand points to 100 on the tachymeter scale. It means that the car is moving at the speed of 100 MPH.

If you drive exactly 1 mile in less than 1 minute, this measurement will tell you exactly how many miles an hour your object is moving. If the second hand points to 120 miles, it means you are going 120 miles per hour.

How to measure speed if object takes more than 1 minute to cover a mile?

Now let’s do some calculations.

If the object took more than 1 minute to travel that distance, you should divide the time by 2 until the measurements are less than 1 minute and less than 1 hour. If the car covered the mile in 75 seconds, the tachymeter would show 240, which is clearly wrong.

But halving the time 75/2 gives us 37.5 seconds, less than a minute. 37.5 seconds on the tachymeter means 100. Divide that in half to get the true speed of the car, 50 miles per hour. Similarly, if you’re measuring something smaller than a perfect unit, you need to divide.

To measure the time it takes to travel 0.5 miles, divide the tachymeter scale by 2. 1/4 mile is divided by 4.

Now that you know how to measure speed, let’s convert it to distance.

How to measure distance using watch tachymeter?

Measuring distance with watch tachymeter

Measuring distance with a tachymeter is much easier than measuring speed.

To measure distance, you need to know your speed.

If the speed is known, start measuring with the second hand at noon and keep on measuring as you are driving.

When the second hand reaches the tachymeter scale corresponding to your speed, you have traveled one unit of distance.

So if you are traveling at 80 miles per hour and the second hand on the tachymeter scale moves to 80, you have traveled 1 mile.

Unfortunately this does not work for acceleration and deceleration. Your speed should be constant.

Watch tachymeter looks a little complicated when one use it for the first time. But it is really a useful tool to measure speed and distance.

If you want to read about more features in watches, see this article.

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