what does a tachometer (tachy-?) really do on a wristwatch ? How do
they work-if they do ?!

Dear Perlu,

Thank you for your inquiry about watch tachometers!

According to experts, a Tachometer, or Tachymeter, quite simply is a
function on a watch that allows the user to measure speed.

A Tachometer is a feature found on some chronograph watches, which
measures the speed at which the wearer has traveled over a measured
distance.  In matchmaking, a timer or chronograph with a graduated
dial on which speed can be read off in kilometers per hour or some
other unit.

For example, the tachometer division on the dial of a chronograph
serves to measure the speed, e.g. of a car on a measured course of 1
km or 1 mile. At the moment the car passed the starting point of the
course, the chronograph is set and stopped at the final point of the
course. The position of the stopped hand on the tachometer scale
corresponds to the speed in km (miles) per hour. The speed over the
whole test run must be the same.

This information was found at:

FotoWatch
http://www.fotowatch.com/glossary.htm#T
Watch information from A to Z
http://www.clockworks.com/watchaz3.html

A site that advertises -  “Call our experts” – 1 800 222 0077
World of Watches 
http://www.worldofwatches.com/

Search terms used:
Tachometer
Watch tachymeter
Wristwatch vocabulary

Thank you and have a great day!

Best Regards,
Skis4jc

A stopwatch with tachometer is very useful. For example, to measure
the speed of a formula 1 race car, the time to cover a distance of
1000 meters is measured, and the tachometer scale automatically
indicates the speed in kilometers per hour. A chrono that made
particular good appearance in the racing world is the Rolex Cosmograph
Daytona. It has a tachometer and a telemeter scale, as well as minute
and hour registration

Thanks ! I am confused at a higher level! NO-Greeat comments ,thanks again ! /Per

Perlu - I *think* what you might be asking is how does the mechanics
of a tachometer work?

I assume it's based on how pedometers work - these just measure
distance.  They work because when you run, at every step your body
jolts up and down.  They have a sensitive switch that will click on
one more jolt with every step.  Then you tell it how much ground you
cover with that one step/pace.  It counts how many steps you take and
multiplies that by how far you cover.  (If 1 pace = 1 yard, then 10
paces = 10 yards.)

Now it knows how far you've travelled (eg 10 yards) (that's the
pedometer bit).  To turn this into a tachometer it also measures how
long it took you to go "the full 10 yards".  It divides 10 by the time
taken (eg 5 seconds), giving you 2 yards per second.


Oh yeah - a pedometer relies on the human jolting a switch with every
footstep.  Tachometers/odometers in a car or bike wouldn't count
footsteps, they would count how many times one of the wheels does a
full turn.  If every full revolution of a wheel means the car/bike has
moved 5 feet, then it multiplies the number of revolutions by 5.


Hopefully that will give you an understanding at a lower level!


Richard - London, UK