A chronograph is a professional term, where "chrono" in Old English and Latin means "time," and "graph" in English represents "recording instrument." [Tudor Watches] This article explores an alternative method of opening the watch movement, hoping it will be useful to everyone. Ordinary watches continuously indicate the passage of time. Chronographs are different; they can record the duration of any given period. Standard chronographs have either 30-minute or 12-hour timing functions. The central second hand on the surface usually stays at zero when idle. To show that the watch is running, most add a constantly moving small second hand. Chronographs come in two types: one type is a standard chronograph with only one measurement object, and another type is a split-seconds chronograph with two measurement objects.
Generally speaking, chronographs are divided by design into single-second hand, double-second hand, single-button, or dual-button structures. In terms of dial design purposes, the most common ones measure speed, such as OMEGA's Moonwatch, ULYSSE NARDIN's pulse watch for measuring heart rate, and TISSOT's JANEIRO chronograph that measures both distance and speed, like radar watches. To distinguish between their functions, simply look at the English inscriptions around the dial. For example, TACHYMETER (speedometer), TELEMETER (range finder), PULSATIONS (pulse measurement function). In fact, operating a chronograph is entirely the same; the difference lies only in the scale. Different scales indicate different functions, but most common chronographs still primarily measure speed.
The most common calculation scale system in chronographs is typically located on the outermost part of the dial or on the bezel of the case, like Omega Speedmaster watches. The main principle is this: knowing a certain unit distance, for instance, 1 kilometer or 1 mile, when a moving object starts within this distance, activate the start function of the chronograph. When the object completes the unit distance, press the stop button. The speed of the object is indicated by the position of the needle. If the scale system is designed for a single lap, then the chronograph becomes effective when the object's speed is below 60 km/h. Chronographs with spiral-designed scales do not encounter ordinary wristwatches with stopwatch functions. The bezel of these watches has sequentially decreasing numbers like 500/400/350, representing speed in units of kilometers per hour. This bezel is called a TACHYMETER (speedometer). For example, if a car travels at a fixed speed of 1 kilometer or 1 mile, using the car speed measurement method, start the timer when the car passes a roadside mileage marker. Stop the timer when the car reaches the next mileage marker. The position where the timer needle stops on the speedometer scale equals the car's speed. If the car covers 1,000 meters in 45 seconds, it converts to a speed of 80 kilometers per hour.