Watches have a number of different options available to regulate their time keeping, and how they measure time. They roughly fall into 2 categories, those with a main spring and a mechanical escapement, or through a quartz crystal and electricity.
Quartz watches are powered by replaceable batteries. They are the most accurate type of watch. Batteries need replacing every few years generally.
Quartz watches work by transmitting an electric current through a specially shaped quartz crystal. This then vibrates at a constant high speed (32,768 times a second), and marks the passage of time using this, which in turn drives the motors for the hour, minute and second hands.
This was first introduced into a production wrist watch in 1969, and revolutionised the watch industry. The main benefit is high accuracy, and normal quartz watches will be accurate to within 30 second a month. Also, it needs infrequent battery changes, instead of needing to always be worn, or always be wound.
Automatic (self winding)
Automatic watches are powered by the movement of the wrist. They store energy generally for 36 hours to 48 hours and therefore require regular wearing, or the watch must be reset after it stops.
This is identical to the mechanical watch in terms of the method of time keeping, through the balance wheel and escapement, and a main spring to store energy. The main difference is that there is a weighted pendulum, or rotor attached to the movement. This spins as the user wears the watch, and is transmitted through to wind the main spring. This was designed so that the watch shouldn't need to be wound by hand by the wearer.
Automatic movements are the most prevalent mechanical watches available, due to the public's demand for a watch that doesn't need to be wound regularly.
Automatic watches often feature lower power reserves than hand wound watches, so they should be worn regularly, or a winding box can be used to ensure the watch is kept wound if you do not wear it every day.
Mechanical (Hand wound)
Mechanical watches are wound by hand, and are often favoured by those who appreciate tradition.
Mechanical watches have existed for centuries, and have the same basic principle. A main spring is wound through the crown to store energy, and this is then unwound, limited to a certain speed by an escapement and balance wheel.
This balance wheel oscillates at a constant speed, most commonly 4 times a second (4Hz), and allows the escapement to unwind the main spring a certain amount at a time.
The unwinding of the spring drives the hands to show the time through a set of gears.
Numerous improvements have been made from the very first watches, so modern mechanical movements are more accurate, and have longer power reserves in the main spring. Despite this, they will need to be wound regularly to keep working, normally once every day or two.
Mechanical watches have lower accuracy than their quartz counterparts, and usually will gain or lose up to 30 seconds a day, depending on how they are worn, and how often the watch is wound.
These should always be taken into account when buying a mechanical watch. The very best grade mechanical watches, are marked as Chronometers. The movements in these are subjected to vigorous independent testing to ensure their time keeping is of a high enough standard. This is carried out at the Official Swiss Chronometer Testing Institute, COSC (Contrôle Officiel Suisse des Chronomètres), and means the watch is accurate to within 4 to 6 seconds a day over a course of 15 days, in a number of different temperatures and positions to ensure the movement is suitable bear the mark.
Solar Powered/Eco-Drive/Tough Solar
Solar powered watches are as accurate as quartz watches and require no battery replacement. They charge by light (even artificial light) and they continue to work even in complete darkness for many months.
This is a quartz watch, using the same system quartz crystal maintaining the timekeeping. The main difference is the inclusion of a solar panel under the dial or on the face of the watch, which collects light from the environment, in many cases artificial as well as natural, and converts it into electrical charge, which is used to recharge a battery or capacitor to run the watch. This helps negate the need to change the battery, and in turn helps the environment as there is no harmful chemicals that need disposal with each battery change. The energy stored in the cell then stops the watch from stopping or losing time when it is not exposed to light.
Tough Solar is Casio's system of time keeping, using a normal quartz crystal as a base. The watch also has a solar feature, similar to the Eco-Drive and other Solar watches. Many of the watches from Casio feature Wave Ceptor technology, which receives the radio time signal from transmitters located worldwide, to set the time to the most accurate possible time. The Tough aspect of the Tough Solar is a unique system that uses a light beam under the dial, deep within the movement, that checks the alignment of the hands. In case of a serious shock, the hands can be instantly reset to the correct time.
This is a quartz watch, with the addition of a rotor that in turns spins to generate electric current to recharge a capacitor or battery. Kinetic has been made famous by Seiko as their brand name for the system, and is the most widely known using this movement type.
Bulova launched this concept, designed with the highest possible precision in mind. The movement is a quartz watch, but features a specially designed quartz crystal, that resonates at 8 times the speed of a normal quartz watch, at 262144Hz. The second hand moves 16 times a second, for a near perfect sweep, as opposed to the 4 times a second sweep of a normal mechanical watch or once every second with a standard quartz watch. The accuracy increase from the higher frequency quartz crystal is noticeably higher than a standard quartz watch, rated at a variance of less than 10 seconds a year. This is the very highest accuracy available for a watch available today with the exception of radio controlled watches.
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