DIFFERENT MEASUREMENTS AND THEIR UNITS
Whether dimensional, angular, electrical, optical, or related to time, measurements are essential in watchmaking manufacturing processes. They themselves work as instruments capable of compiling numerous measurements. In watchmaking, units of measurement are often adapted and calibrated to the industry’s specific needs.
TIME
Whether indicating time or measuring a defined period, be it long or extremely short, time measurement employs a wide range of units of measurement. Even the division of the hour can change and become decimal in specific cases. We address here the units most commonly encountered in watchmaking.
LENGTH AND ANGLES
Contrary to most industries, the unit of length measurement used in watchmaking is the millimetre. This choice was made due to the limited dimensions of a watch, its components, and the precision they require. Angular measurements are traditionally expressed in degrees and all their subdivisions (angular minutes, angular seconds, etc.).
MASS
Some components must be lightweight, while others are heavy. Some must be balanced, while others need not be. Mass and inertia are values constantly present in watchmaking regardless of production methods or a component’s nature.
TEMPERATURE
In many manufacturing processes, strict temperature control is essential. Temperature and its variations also have a significant impact on the mechanism of a watch (especially mechanical ones). Depending on the situation, Celsius, Fahrenheit, or Kelvin units can be used, requiring a high level of precision and advanced measurement technology. In other cases, measurements may be more empirical. For example, the temperature of tempering is evaluated by the eye based on the colours the steel takes on as its temperature rises (e.g., straw yellow = approx. 230°C, dark blue = approx. 288°C).
FREQUENCY
This is the number of times a periodic phenomenon repeats within a defined duration. In watchmaking, the most common frequency measurement is that of the oscillator. This is commonly expressed in two distinct units: the number of alternations per hour (A/h) or the number of oscillations per second (Hertz, Hz). For example, 18,000 A/h is equal to 2.5 Hz.
AMPLITUDE
Amplitude represents the difference between the extreme values of a quantity (a wave). In watchmaking, the accuracy of a watch depends on the amplitude of the oscillator. It refers to the angle travelled by the balance wheel from one end of its swing to the other. This is expressed in degrees of arc (°).
ELECTRICAL MEASUREMENTS
While there is, by definition, no electrical presence in a mechanical watch, electricity and electronics are present in most time measurement devices. The first electric clocks were produced in the first half of the 19th century. Today, some clocks and watches are occasionally equipped with hybrid movements (electro-mechanical). Electricity powers the workshops, and some machines use electricity as a tool. For example, an electric arc cuts material in electrical discharge machining or welds two parts of tweezers together. And an electric current “carries” material during electroplating processes. Electrical measurements are thus omnipresent in modern watchmaking, whether artisanal or industrial.
HARDNESS
The hardness of a material determines many characteristics of a component: its resistance to wear, shock, or scratches, and its coefficient of friction. As a rule, a tool must be harder than the material it works on. Hardness is an essential criterion for the functional properties of a component as well as for the means required to manufacture it. Many units of measurement exist and are used, as do many standardized hardness test methods.
LIGHT
Light is present at various stages or processes of manufacturing. It is used in chemical etching methods, photolithographic processes (DRIE etching, UV-LIGA), or to polymerise an adhesive or composite lacquer. Optics is mainly applied in dimensional control when it comes to production. Concerning the watch itself, measurements related to optics and light specifically concern the displays (intensity of a luminescent material, UV resistance, refraction, diffraction, etc.).
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