What is a TACHYMETER (TACHYMETRE) scale and how does it work?
A. WHAT IT DOES The tachymetre scale can be used to compute many things, but it’s primary purpose is to compute the speed after noting how long it takes to travel a fixed distance (e.g. one mile or kilometer). The dial is a scale which computes the function: Tachymetre Dial = 3600 / Elapsed Time in Seconds The scale is valid for all elapsed times from 7.2 seconds to 60 seconds. If the duration of the event is outside this range, then the answer on the dial is invalid. HOW TO USE IT For example, suppose you wanted to measure the average speed a racecar was traveling. After starting the chronograph function when the car passes the starting line, and stopping it after the car travels exactly one mile, you note that the chronograph hand is pointing at the 4 o’clock position (i.e. 20 seconds have elapsed) Looking beyond the 4 to the Tachymetre dial reveals the chronograph hand pointing at 180. This means that the average speed of the car would be 180 MPH. Let’s say, instead of the race car
