The need to measure the time it came with the development of agriculture. Farmers used to determine the best timing system and periods were primitive lunar calendars.
The Egyptians were the first to develop a way to say in general the time with calendars and clocks. Around 2800 BC, had established a 365-day calendar, based on his observations of the rising and setting of bright stars like Sirius and the annual flooding of the Nile, whichits agriculture is based. By 2100 BC the Egyptians had devised a way to divide the day into 24 hours. Almost simultaneously, made the first sundials or shadow clocks to measure time during the day. A sundial indicates the time of day from the position of the shadow of an object on which the sun's rays fall.
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Since 1500 BC the Egyptians had invented another, more precisely, how to tell time, the water clock or hourglass, which uses the constant drip of water from a ship to conductmechanical device that indicates the time.
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While astronomers of Babylon "about the water clock, taking into account the equation of time caused by the distance that varies between the Earth and the movement of the sun in an elliptical orbit. Because of this effect could be noon until half ' hours before or after the time when the sun is high in the sky.
Around 270 BC, Alexandria Ctesibus engineer designed water clocks rang bells, puppets moved and caused mechanical birds to sing.The water clock remained in use until the development of mechanical watches is about 3,000 years later.
The measurement of time intervals, however, was possible with the hourglass. The search for precision watches began with the growing trade in the Middle Ages and the first fruits of the scientific revolution. This need for mechanical clocks measure time with simple weighted pendulums. But these were not portable.
The first watches
The invention ofspring and the escapement mechanism, has ushered in the era of portable clocks. The flight is a mechanism that controls and limits the cancellation of the watch, converting what would have been a simple reversal, in an energy-controlled press and magazines. The exhaust makes a change, simply blocking that passes between a "driven" and a "free state" with an unexpected end of each cycle. The discharge for the same reason also occursticking noise characteristic of mechanical watches.
Another mechanical method is the mechanism wheel balance. The wheel balance with the balance spring (also known as spiral) - it is a simple harmonic oscillator, which controls the movement of the gears of the clock system similar to the pendulum of a grandfather clock. This is possible because the moment of inertia of the wheel is fixed, and the wheel as a whole provides a regular motionthe period known. These clocks to produce a clicking sound.
Purely mechanical watches are still popular. The high level of craftsmanship of purely mechanical watches is much of its charm. Compared to electronic movements, mechanical watches are inaccurate, often with errors of seconds per day. They are often sensitive to the location and temperature, which are expensive to produce, they need regular maintenance and adjustment, and much moreprone to failure.
Further accuracy was achieved in the sixties by Diapason watches, which use a fork at a precise frequency (360 Hz in most cases) to drive a mechanical watch. Since the fork is used instead of a typical steering wheel, these watches naturally hum instead of dialing. Fork adjustment electromechanical movements. The task of converting the vibrations into electronic impulses of rotation of the fork is done via two tiny fingers precious stones, called pawls, one of which is connected to one of the prongs of the tuning. As the fork vibrates, the pawls precisely ratchet a tiny index. This wheel has teeth more than 300 indexes barely visible and runs more than 38 million times a year. Small electric coils that drive the tuning fork have 8000 turns of insulated copper wire with a diameter of 0.015 mm and a length of 90 meters. This feat of engineering was a prototype in 1950 and early 60s.
Advent of electronic quartz> View in 1969
In 1948, Max Hetzel uses an electronic device, a transistor to create the first electronic watch. This development has become obsolete with the use of a quartz crystal that has met in quartz watches, which use the piezoelectric effect in a tiny quartz crystal to provide a stable time for a mostly electronic movement: the crystal quartz oscillator which resonates at a specific frequency and very stable, and that can be used to accuratelyrhythm of a timing mechanism. These movements are primarily electronic drive mechanical hands on the clock. Quartz movements are ten times better than a mechanical movement.
Innovations introduced the following types of clocks:
Manual watches
In the user watches the spring must be rewound by the user periodically by turning the crown clockwise.
Rope or automatic watches
A stringor an automatic mechanism that rewinds the main cause of a mechanical movement of the body's natural movements of the wearer.
Kinetic Quartz or automatic
Some electronic watches are also powered by the wearer of the watch movement. Kinetic powered quartz watches use the arm movement of the user to convert a rotating weight, which turns a generator to charge a rechargeable battery power that the works' clock. The conceptis similar to the movements of the automatic loading of the spring, with the exception that the electricity is generated instead of mechanical spring tension.
Battery-powered clock in 1957
Electronic watches require electricity as an energy source. Some mechanical movements and hybrid electronic mechanical movements also require electricity. Usually, electricity is supplied by a replaceable battery. Watch batteries (strictly speaking cells) are specially designed forpurpose. They are very small and provide small amounts of power continuously for long periods of time (several years or more). Mercury Batteries hostile environment gave way to silver oxide and lithium. Cheap batteries may be alkaline, the same size as silver oxide, but to provide a shorter life. Rechargeable batteries are used in some sundials.
Solar-Powered Watch
Some electronic watches are powered by light. A photovoltaic cell inface of the watch converts light into electricity, which in turn is used to recharge a rechargeable battery. The watch movement is powered by rechargeable battery. While the watch is regularly exposed to light strong enough (such as sunlight), replace the battery, and some models need only a few minutes of sunlight to provide weeks of energy.
Some of the early solar watches of 1970 has a unique and innovative designaccommodate the wide range of solar cells needed to power them (Nepro, and some models Cristalonic Sure, Alba, Seiko and Citizen). Over the decades progressed and the efficiency of solar cells increased while the power requirements of the movement and display decreased, solar watches began to be designed to look like other conventional watches.
Radio-controlled movements
Some electronic quartz watches are able to synchronize with an external timesource. These sources include the time of radio signals directly driven by atomic clocks, time signals from GPS navigation satellites, the German DCF77 signal in Europe, WWVB in the U.S., and others. These watches are not run most of the time, but periodically align with the external time source automatically chosen, usually once a day.
Since these watches are regulated by an external source of high-precision time, never off by more thana small fraction of a second per day (depending on the quality of their quartz movements), provided that can receive external time signals that they expect. Moreover, its long-term accuracy is comparable to the external time signals they receive, in most cases (eg GPS signals and special radio broadcasts of time based on atomic clocks) is better than a second in three million years. For all practical purposes, the radio-controlled wristwatches keep nearperfect timing.
The movements of this kind not only synchronize the time of the day, but also the date, the state of leap year this year and the current state of daylight saving time (on or off). They get all the information they receive external signals. Because of this continual automatic updating does not require manual configuration or replacement.
A disadvantage of radio-controlled movements is that you can not synchronize if radio reception conditions is poor.Even here, however, simply run autonomously with the same accuracy as a normal quartz watch until they are next able to synchronize.
Clock display
In the seventies, two types of screens have been developed.
Analog display
A numbered dial on which are mounted at least a rotating hour hand and be one, turning the minute hand. Many watches also incorporate a third hand that shows the current minute of the second current. Watchespowered by quartz have second hands that break every second to the next marker. Watches powered by a mechanical motion that a "second hand", the name comes from its uninterrupted smooth (radical) movement through the markers The hand moves in small Only steps away, usually 1 / 6 of a second, which corresponds to the beat of the bar. All hands are normally mechanical, physically rotating on the dial, although a few watches have been produced with "hands"which are simulated by a liquid crystal display.
The digital
A digital display shows the time as just a number, for example, 00:40 instead of a symbol that indicates the number 12 and a hand always points to the number 8 on the dial.
LED displays have been replaced by (LCD) that uses less battery power and were much more convenient to use with the display always visible and no need to press a button to see the first time.
Since 1980, technologyDigital clocks have greatly improved. They added new features every year.
1982 Seiko produced a watch with a built in small-screen TV
1983 Casio produced a digital clock with thermometer and see another that could translate 1,500 Japanese words into English
1985 has produced the calculator Casio CFX-400 scientific clock.
1987 Casio produced a watch that can call the phonethe number and the city would react to his voice.
1995 Timex release a watch that allows users to download and store data from a computer on the wrist.
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