Clock

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The clock is a tool for measuring, storing, and showing the time. The clock is one of the oldest human inventions, which meets the need to measure shorter time intervals than natural units: day, lunar month, and year. Devices that operate on several physical processes have been used for thousands of years.

Some predecessors to the modern clock can be regarded as "clocks" based on movement in nature: A clock denotes time by displaying the position of the shadow on a flat surface. There are various timer durations, the famous example is the hourglass. The water clock, along with the sun hour, is probably the oldest time gauge. A major advance occurred with the discovery of the breakout threshold, which allowed the first mechanical clock to be about 1300 in Europe, which saves time by oscillating timers like a balance wheel.

Lost silent instruments such as the striking mechanism have traditionally been known as watches . In the current general usage, "clock" refers to any device to measure and display the time. Other watches and watches that can be carried on a person are often distinguished from the clock. Spring-driven clocks emerged during the 15th century. During the 15th and 16th centuries, hours flourished. Subsequent developments in accuracy occurred after 1656 with the discovery of the pendulum clock. The main stimulus to improve the accuracy and reliability of the clock is the importance of keeping the right time for navigation. The electric clock was patented in 1840. The development of electronics in the 20th century caused a clock without any clockwork at all.

The element of timing in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates at a particular frequency. These objects may be pendulums, tuning forks, quartz crystals, or electron vibrations in atoms when emitting microwaves.

The clock has a different way of displaying the time, connected to the internal clock type: Analog clock usually shows the time using angles. The digital clock displays the numerical representation of time. Two numerical display formats are commonly used in digital clocks: 24 hour notation and 12 hour notation. Most digital clocks use electronic and LCD, LED, or VFD mechanisms. For comfort, distance, phone or blindness, the auditory clock presents the time as a sound. There are also hours for blind people who have displays that can be read using the sense of touch. Some are similar to normal analog screens, but are built so that the hand can be felt without destroying it. The evolution of clock technology continues today. The study of timeliness is known as horology.

Video Clock

History

Etymology

The word hour was derived (through Dutch, French North and Latin Medieval) from the words Celtic clagan and clocca meaning "bell".

Maps Clock

Time meter

Sundial

The clear Sun position in the sky moves along the road each day, reflecting the Earth's rotation. Shadows cast by stationary objects move simultaneously, so their position can be used to indicate the time of day. A solar clock denotes time by displaying the position of the shadow on a flat surface (usually), which has clock-appropriate markings. Sundials can be horizontal, vertical, or in other orientations. Sundial is widely used in ancient times. With knowledge of latitude, a well-built sun watch can measure local sun time with reasonable accuracy, in a minute or two. Sundial continues to be used to monitor clock performance until the modern era. However, practical limitations, such as a sundial only work well on relatively clear days, and never at night, encourage the development of other techniques for measuring and timing. The Jantar Mantar In Delhi and Jaipur is an example of a sundial. They were built by Maharaja Jai ​​â € <â € Devices that measure the duration, time and interval elapsed

Many devices can be used to mark the passage of time regardless of reference time (time, minutes, etc.) and can be useful for measuring duration or interval. Examples of such timers are the candlesticks, the hours of incense and the hourglass. Candle clocks and incense clocks work on the same principle where resource consumption is more or less constant allowing accurate and repeatable estimates of the time portion. In an hourglass, fine sand flowing through a small hole at a constant rate indicates a random, pre-determined time course. Resources are not consumed but reused.

Water

The water clock, also known as clepsydrae (sg: clepsydra ), together with the sunlight, may be the oldest time gauge, with the only exception being the vertical gnomon and the counting of the wand counting days. Given their immense antiquity, where and when they first exist is unknown and may not be known. The bowl-shaped stream is the simplest form of water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water hours, but the earliest dates are less certain. However, some authors wrote about the water clock that emerged since 4000 BC in these regions of the world.

The Greek astronomer Andronicus of Cyrrhus oversaw the construction of the Wind Tower in Athens in the 1st century BC. Greek and Roman civilization is credited for initially developing a water clock design to incorporate intricate gearing, which connects to fantastic automata and also results in increased accuracy. This progress is continued through Byzantium and the times of Islam, eventually making their way back to Europe. Independently, the Chinese developed their own sophisticated water clock (??) at 725 A.D., passing on their ideas to Korea and Japan.

Some water clock designs are developed independently and some knowledge is transferred through the spread of trade. Pre-modern societies do not have the exact exact timing requirements that exist in modern industrial societies, where every working hour or break is monitored, and work can start or end at any time apart from external conditions. In contrast, the water clock in ancient societies is used primarily for astrological reasons. This initial water clock is calibrated with a sundial. Although it never reached the level of accuracy of modern watches, the water clock was the most accurate and commonly used time meter for thousands of years, until it was replaced by a more accurate pendulum clock in seventeenth-century Europe.

Islamic civilization is credited with advancing the accuracy of the clock with complicated techniques. In 797 (or perhaps 801), the Abbasid Caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian elephant named Abul-Abbas along with an "exemplary example" of the water clock. Pope Sylvester II introduces hours to northern and western Europe around 1000AD

In the 13th century, Al-Jazari, an engineer from Mesopotamia (living in 1136-1206) who worked for the Artuqid king of Diyar-Bakr, Nasiruddin, made many hours in various shapes and sizes. A book about his work illustrates 50 mechanical devices in 6 categories, including water hours. The most famous clocks include the Elephant clock, Scribe and Castle, all of which have been successfully reconstructed. As well as telling of time, these magnificent hours are a symbol of the status, splendor and wealth of the Urtuq State.

Initial mechanics

The word horologia (from Greek ???, jam, and ??????, to tell) is used to describe the initial mechanical clock, but the use of this word (still used in some Romance languages) for all timers hide the true nature of the mechanism. For example, there is a note that in 1176 the Sens Cathedral installed a 'horologe' but the mechanism used was not known. According to Jocelin of Brakelond, in 1198 when a fire at St Edmundsbury monastery (now Bury St Edmunds), the monks ran into the clock 'to fetch water, indicating that their water clock has a reservoir large enough to help quench the fire occasionally. The word hour (from the Celtic words clocca and clogan , both means "bell"), which gradually replaces "horologe", indicating that is a bell sound that also marks the prototype clockwork that emerged during the 13th century in Europe.

Water-made cogwheel clocks were made in China in 725 by Yi Xing and Liang Lingzan. This was not considered a breakout mechanism mechanism because it was not unidirectional, the Song polymath dynasty and the Su Song genius (1020-1101) incorporated it into the monumental innovation of the Kaifeng astronomical clock tower in 1088. The astronomical clock and circular arm rotary circle still depended on the use of running water during spring, summer, autumn and liquid mercury during winter freezing temperatures (ie hydraulics). The hours of mercury, described in Libros del saber , Spanish works of 1277 consisting of translations and paraphrases of Arabic works, are sometimes cited as evidence of Muslim knowledge of mechanical clocks. The mercury-powered cogwheel clock was created by Ibn Khalaf al-Muradi

In Europe, between 1280 and 1320, there is an increase in the number of references to clocks and horologists in church records, and this may indicate that a new clock type mechanism has been created. The existing clock mechanisms that use water strength are being adjusted to take their driving force from falling loads. This power is controlled by some form of oscillating mechanism, probably derived from a ringing device or an existing alarm. The release of this controlled power - escape - marks the beginning of the actual mechanical clock, which is different from the cogwheel clock mentioned earlier. Break the breakout mechanism inherited in actual mechanical clock spikes, which require no fluid strength, such as water or mercury, to work.

These mechanical hours are intended for two main purposes: for signaling and notifications (eg service time and public events), and for modeling the solar system. The first objective is administrative, the latter emerging naturally given the scientific interest in astronomy, science, astrology, and how these subjects were integrated with religious philosophy at the time. Astrolabs are used by both astronomers and astrologers, and it is natural to apply clockmoving to a rotating plate to produce a working model of the solar system.

A simple clock meant primarily for notices installed in the tower, and not necessarily requiring a face or a hand. They will announce canonical clocks or intervals between set filming times. Canonical clocks vary in length as the sun rises and sunsets shifts. More sophisticated astronomical clocks will have fast movements or moving hands, and will show time in various time systems, including the Italian clock, canonical clock, and time measured by astronomers at the time. Both clock styles begin to acquire luxurious features such as automata.

In 1283, a large clock was installed in Dunstable Priory; its location above the rood screen indicates that it is not a water clock. In 1292, Canterbury Cathedral installed a 'great horloge'. For the next 30 years there was a mention of clocks at a number of ecclesiastical institutions in England, Italy and France. In 1322, a new clock was installed in Norwich, an expensive substitute for the previous clock installed in 1273. It has a large astronomical dial (2 meters) with automata and bells. Installation costs include full-time work of two hour keepers for two years. Astronomy

In addition to the Chinese astronomical clock Su Song in 1088 mentioned above, in Europe there were hours built by Richard of Wallingford at St Albans in 1336, and by Giovanni de Dondi in Padua from 1348 to 1364. They ceased to exist, but detailed descriptions of their design and construction survive, and modern reproductions have been made. They illustrate how quickly mechanical clock theory has been translated into practical constructs, and also that one of the many impulses for their development has been the desire of astronomers to investigate the phenomenon of space.

The Wallingford Clock has a large astrolabe dial type, showing the sun, moon age, phases, and knots, star maps, and possibly planets. In addition, it has a wheel of fortune and a tidal state indicator on the London Bridge. The bells rang every hour, the number of strokes showing the time. The Dondi clock is a seven-sided construction, 1 meter high, quickly indicating the time, including minutes, the movement of all known planets, the automatic calendar of fixed and moving parties, and the prediction of the eclipse of the hand rotates once every 18 years. It is not known how accurate or reliable these hours are. They may be manually adjusted daily to compensate for errors caused by improper wear and tear. Water hours are sometimes still used today, and can be checked in places like castles and ancient museums. The Salisbury Cathedral Clock, built in 1386, is considered to be the world's oldest mechanical clock that strikes the clock.

Spring-driven

Clock makers develop their art in various ways. Building a smaller clock is a technical challenge, such as increasing accuracy and reliability. Clocks can be impressive displays to show skilled craftsmanship, or cheaper, mass produced products for domestic use. Specific release is an important factor that affects the accuracy of the clock, so many different mechanisms are attempted.

Spring-pushed clocks emerged during the 15th century, although they were often wrongly credited to Nuremberg's Peter Henlein (or Henle, or Hele) maker about 1511. The earliest springtime available was the space clock given to Phillip who Well, Duke of Burgundy circa 1430, now at the Germanisches Nationalmuseum. The spring power that jammers present with new problems: how to keep the clock's movement running at a constant level as the springs run. This resulted in the discovery of stackfreed and fusee in the fifteenth century, and many other innovations, to the discovery of the modern going barrel in 1760.

Initial call calls do not show minutes and seconds. The clock with a dial showing the minutes is illustrated in the 1475 manuscript by Paul Almanus, and several hours of the 15th century in Germany show minutes and seconds. The earliest records of the second hand on a clock date back to about 1560 hours which is now in the Fremersdorf collection.

During the 15th and 16th centuries, clocks flourished, especially in the metalworking cities of Nuremberg and Augsburg, and in Blois, France. A few more basic clock hours have only one hand timer, with dial between hour markers divided into four equal parts making the hours readable to the nearest 15 minutes. The other hour is an exhibition of skills and skills, combining astronomical indicators and musical movements. The cross-beat escape was invented in 1584 by Jost BÃÆ'¼rgi, who also developed the remontoire. Clock BÃÆ'¼rgi is a great improvement of accuracy because they are correct in one minute a day. These hours helped 16th-century astronomer Tycho Brahe to observe astronomical events with much higher precision than before.

Pendulum

Subsequent developments in accuracy occurred after 1656 with the discovery of the pendulum clock. Galileo had the idea of ​​using a swinging bob to set the timekeeping movement at the beginning of the 17th century. Christiaan Huygens, however, is usually considered the inventor. He determined the mathematical formula associated with the length of the pendulum to time (about 99.4 cm or 39.1 inches for one second movement) and had the first pendulum-driven clock created. The first model clock was built in 1657 in The Hague, but in England the idea was taken. The big clock (also known as the grandfather clock) was made to accommodate the pendulum and worked by British clockmaker William Clement in 1670 or 1671. At that time also clock cases began to be made wooden and facial clocks to utilize hand-painted enamel and ceramics.

In 1670, William Clement created an anchor escape, an increase over the Huygens crown pruning. Clement also introduced suspension pendulum suspension in 1671. The minute concentric hand was added to the clock by Daniel Quare, the London watchmaker and others, and second-hand was first introduced.

The hair springs

In 1675, Huygens and Robert Hooke found spiral balance spirals, or hair springs, designed to control the speed of oscillating the balance wheel. This important advance has finally made an accurate pocket watch possible. The great British clockmaker, Thomas Tompion, was one of the first to successfully use this mechanism in his pocket watch, and he adopted a minute hand which, after various designs were piloted, was finally stabilized into a modern configuration. The striking shelf and snail mechanisms for striking hours, introduced in the 17th century and have different advantages over the 'countwheel' (or 'locking plate') mechanism. During the twentieth century there was a common misconception that Edward Barlow found the shelf and snail stark. In fact, his invention is connected with repetitive mechanisms using shelves and slugs. The repetitive clock, which chronicles the number of hours (or even minutes) was created by Quare or Barlow in 1676. George Graham found a deadlock escape for hours in 1720.

Marine Kronometer

The main stimulus to improve the accuracy and reliability of the clock is the importance of keeping the right time for navigation. The position of a ship at sea can be determined with reasonable accuracy if a navigator can refer to a lost or earned clock of less than about 10 seconds per day. This clock can not load a pendulum, which is almost useless on a rocking ship. In 1714, the British government offered a large financial reward with a value of 20,000 pounds, for anyone who could accurately determine longitude. John Harrison, who devoted his life to improving the accuracy of his watch, then received a large sum under the Longitude Act.

In 1735, Harrison built his first chronometer, which was constantly repaired for the next thirty years before sending it for review. The clock has many innovations, including the use of bearings to reduce friction, a weighted balance to compensate for the slope and roll of ships at sea and the use of two different metals to reduce the problem of expansion of heat. The chronometer was tested in 1761 by Harrison's son and at the end of 10 weeks the clock was in error of less than 5 seconds.

Mass production

Britain has been dominating in watchmaking for most of the 17th and 18th centuries, but maintains a production system directed to high-quality products for the elite. Despite attempts to modernize the clock-making with mass production techniques and the application of duplicate tools and machinery by the British Watch Company in 1843, it was in the United States that the system was taking off. In 1816, Eli Terry and several other Connecticut clockmakers developed a mass-producing way of hours using interchangeable parts. Aaron Lufkin Dennison started a factory in 1851 in Massachusetts that also used interchangeable parts, and in 1861 run a successful company incorporated as Waltham Watch Company.

Initial power

In 1815, Francis Ronalds published the first electric clock powered by dry pile batteries. Alexander Bain, the Scottish watchmaker, patented the electric clock in 1840. The main thrust of the electric clock was injured with electric motors or by electromagnets and armatures. In 1841, he first patented the electromagnetic pendulum. By the end of the nineteenth century, the emergence of dry cell batteries made it feasible to use electricity in hours. Spring or weight driven clocks that use electricity, either alternating current (AC) or direct current (DC), to rewind the spring or increase the weight of the mechanical clock will be classified as an electromechanical clock. This classification will also apply to clocks that use electrical impulses to push the pendulum. In electromechanical clocks the electricity does not work to keep time. These types of clocks are made as individual watches but are more commonly used in synchronized time instalations in schools, businesses, factories, trains and government facilities as main hours and working hours.

The power clock that is turned on from the AC supply often uses a synchronous motor. Flow supplies alternate with frequencies 50 hertz in many countries, and 60 hertz in other countries. The motor rotor rotates at a speed associated with the frequency of change. Appropriate gearing changes this rotation speed to the correct one for analog clockwise. The development of electronics in the 20th century caused a clock without any clockwork at all. The time in these cases is measured in several ways, such as by a change of AC supply, vibration of a tuning fork, quartz crystal behavior, or atomic quantum vibration. The electronic circuit divides this high-frequency oscillation into a slower one that pushes the time display. Even mechanical clocks have since been largely powered by batteries, eliminating the need for winding.

Quartz

The quartz crystalline piezoelectric properties were discovered by Jacques and Pierre Curie in 1880. The first crystal oscillator was invented in 1917 by Alexander M. Nicholson afterwards, the first quartz crystal oscillator was built by Walter G. Cady in 1921. In 1927 the first quartz clock was built by Warren Marrison and JW Horton at Bell Telephone Laboratories in Canada. The next decade sees the development of quartz clocks as a precision time measurement tool in a laboratory setting - a large, refined electronic counter, built with a vacuum tube, limiting its practical use elsewhere. The National Standards Bureau (now NIST) is based on US time standards on quartz clocks from late 1929 until the 1960s, when it turned into atomic clocks. In 1969, Seiko produced the world's first quartz watch, Astron. Inherent accuracy and low production costs result in the proliferation of quartz clocks and watches.

Atom

In the 2010s, atomic clocks were the most accurate clocks available. They are much more accurate than quartz clocks because they can be accurate within seconds for thousands of years. Atomic clocks first theorized by Lord Kelvin in 1879. In the 1930s the development of magnetic resonance created a practical method for doing this. The prototype ammonia maser device was built in 1949 in the US National Bureau of Standards (NBS, now NIST). Though it's less accurate than the existing quartz clock, it serves to show the concept. The first accurate atomic clock, a standard cesium based on a particular transition of cesium-133 atoms, was built by Louis Essen in 1955 at the National Physical Laboratory in England. The calibrated atomic clock calibration calibration is performed by the use of astronomical time scales ephemeris time (ET). In 2013, the most stable atomic clock is the ytterbium clock, which is stable in less than two parts in 1 quintillion ( 2 ÃÆ' - 10 ^-18 ).

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Operation

The invention of a mechanical clock in the 13th century initiated a change in the timing method of a continuous process, such as the movement of a shadow gnomon at a solar clock or a liquid stream in a water clock, to a periodic oscillator process, such as a swing of a pendulum or quartz crystal, more accuracy. All modern clocks use oscillation.

Although the mechanisms they use vary, all oscillating, mechanical, digital and atomic clocks work together and can be divided into analog parts. They consist of objects repeating the same motion over and over again, an oscillator , with a precise time interval constant between each repetition, or 'beat'. Attached to the oscillator is a controller device, which sustains the oscillator's motion by replacing the energy lost due to friction, and converting the oscillation into a series of pulses. The pulse is then calculated by some type of counter , and the count count is converted to a convenient unit, usually seconds, minutes, hours, etc. Finally some sort of indicator displays the result in a human readable form.

Resources

• In a mechanical clock, a resource is usually a load hanging on a string or chain that is wrapped around a pulley, sprocket or drum; or spiral spring called the main thrust. The mechanical clock should be regularly wound, usually by turning the knob or lock or by pulling the free end of the chain, to store energy in weight or spring to keep the clock running.
• In hours of electricity, the power source is a battery or AC power line. In hours that use AC power, a small backup battery is often included to keep the clock running if it is temporarily removed from the wall or during a power outage. Battery-powered analog wall clocks are available that operate for 15 years between battery changes.

Oscillator

The element of timing in every modern clock is the harmonic oscillator, the physical object (resonator) that vibrates or repeats itself at the correct constant frequency.

• In a mechanical clock, this is a pendulum or a balance wheel.
• In some electronic clocks and early watches such as Accutron, it is a tuning fork.
• In quartz clocks and clocks, it is a quartz crystal.
• In atomic clocks, this is the vibration of electrons in an atom when it emits microwaves.
• In an early mechanical clock before 1657, it is a balance wheel or a raw foliot that is not a harmonic oscillator because it has no spring equilibrium. As a result, they are very inaccurate, with errors maybe an hour a day.

The advantage of a harmonic oscillator over another form of oscillator is that it uses resonance to vibrate at its proper natural resonant frequency or 'tap' depending only on its physical characteristics, and refuses to vibrate at another level. The possible precision achieved by a harmonic oscillator is measured by a parameter called its Q, or a quality factor, which increases (other things are equal) with the resonant frequency. This is why there is a long-term trend toward higher frequency oscillators in hours. The balance wheel and the pendulum always include how to adjust the watch rate. Quartz timepieces sometimes include a level screw that adjusts the capacitor for that purpose. Atomic clocks are the main standard, and their numbers are not adjustable.

Synced clock or slave

Several hours rely on the accuracy of the external oscillator; that is, they are automatically synced to a more accurate clock:

• Working hours, used in institutions and large schools from the 1860s through the 1970s, save time with pendulum, but transferred to the master clock in the building, and periodically receive signals to synchronize them with the master, often on the hour. The next version without the pendulum is triggered by pulses of the master clock and a specific sequence used to force a quick sync after a power failure.
• Synchronous power clock does not have an internal oscillator, but calculates a 50 or 60 Hz oscillation cycle from an AC power line, which is synchronized by the utility to a precision oscillator. Calculations can be done electronically, usually in a clock with a digital display, or, in an analog clock, the AC can drive a synchronous motor that rotates the exact fraction of a revolution for each line voltage cycle, and moves the gear. Although changes in the frequency of grid lines due to load variations can cause hours to temporarily gain or lose a few seconds during a day, the total number of cycles per 24 hours is maintained very accurately by the utility company, so the hours make the time accurate for long periods of time.
• Real-time computer clocks save time with quartz crystals, but can be periodically (usually weekly) synchronized over the Internet to atomic clocks (UTC), using Network Time Protocol (NTP). Sometimes a computer on a local area network (LAN) gets its time from one locally managed server accurately.
• The clock radio saves time with quartz crystals, but is periodically synchronized with the time signals sent from a special standard timing radio station or satellite navigation signal, fixed by the atomic clock.

Controller

It has a dual function of keeping the oscillator running by providing a 'boost' to replace the energy lost due to friction, and turning its vibrations into a series of pulses that serve to measure time.

• In a mechanical clock, this is an escape, which gives a proper boost to the swinging pendulum or balance wheel, and releases one gear from the breakout wheel on each swing, allowing all clock wheels to moving forward with a fixed amount with each swing.
• In this electronic clock is an electronic oscillator circuit that provides quartz quivering crystals or a small 'push' tuning fork, and produces a series of electrical pulses, one for each crystalline vibration, called a clock signal./li>
• In the atomic clock the controller is an evacuated microwave cavity attached to a microprocessor-controlled microwave oscillator. A thin gas cesium atom is released into the cavity where they are exposed to microwaves. Lasers measure how many atoms have absorbed microwaves, and an electronic feedback control system called locked phase loop will set the microwave oscillator up to a frequency that causes the atom to vibrate and absorb microwaves. Then the microwave signal is divided by the digital counter to become the clock signal.

In a mechanical clock, low Q of the balance wheel or pendulum oscillator makes them very sensitive to the disturbing effects of breakout impulses, so the runaway has a great effect on the accuracy of the clock, and many runaway designs are attempted. The higher Q resonators in electronic clocks make them relatively insensitive to the disruptive effects of drive strength, so driving oscillator circuits is a much less important component.

Counter chain

It counts the pulse and adds it to get the traditional time unit seconds, minutes, hours, etc. It usually has a condition to set hours by manually entering the exact time to the counter.

• In this mechanical clock is done mechanically by a dental gear, known as the train wheel. The gear cart also has a second function; to transmit mechanical power from the power source to run the oscillator. There is a frictionless friction called 'pine cannon' between the gears that move the hand and the rest of the clock, allowing the hand to rotate to set the time.
• In digital clocks, integrated circuit counters or circuit breakers add digital pulses, using binary logic. Often the pushbutton on the chassis allows clock and minute counters to increase and decrease to set the time.

Indicator

It displays seconds, minutes, hours, etc. In human readable form.

• The earliest mechanical clock of the 13th century lacked a visual indicator and marked the time that a striking bell could hear. Many hours to this day are striking hours that strike the clock.
• The analog clock displays the time with the analog clock display, which consists of a round rotary dial with numbers 1 to 12, hours in a day, around the outside. The clock is shown with one watch, which makes two turns in a day, while minutes are represented by one minute, which makes one revolution per hour. In a mechanical clock, dental gears move their hands; in an electronic clock the circuit produces a pulse every second that drives the stepper and gear motors, which move the hand.
• The digital clock displays the time in digits that change periodically on the digital display. A common misconception is that digital clocks are more accurate than analog wall clocks, but these types of indicators are separate and irrespective of the accuracy of the time source.
• Speaking hours and the speaking clock service provided by the telephone company speak audible time, using digitally recorded sound or synthesized.

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Type

Clocks can be classified by time display type, as well as by timeliness method.

Time display method

Analog

An analog clock typically uses a face clock that shows the time using a rotating pointer called "hand" on a dial or a fixed numbered dial number. The face of a standard clock, universally known throughout the world, has a short "watch" showing clocks in a 12-hour circular cycle, making two revolutions per day, and longer "pointed needles" showing minutes in the clock stream on the dial. same, which is also divided into 60 minutes. It may also have a "second hand" showing seconds in the current minutes. The only widely used clock display today is the 24-hour analogue dial, due to the 24 hour use within military organizations and schedules. Before modern day clock faces were standardized during the Industrial Revolution, many other face designs were used over the years, including dial divided into 6, 8, 10, and 24 hours. During the French Revolution, the French government tried to introduce a 10-hour clock, as part of a decimal-based metric-measurement system, but to no avail. The 6 hour Italian clock was developed in the 18th century, presumably to save power (hours or hours striking 24 times using more power).

Another type of analog clock is the sun clock, which tracks the sun continuously, taking time with its gnomon shadow position. Since the sun does not adjust to summer time, the user must add an hour during that time. Correction should also be made for the time equation, and for the difference between the longitude of the hour and the center meridian of the time zone used (ie 15 degrees east of the prime meridian for each hour that the time zone precedes GMT). Sundial uses some or part of a 24-hour analog dial. There are also clocks that use digital screens despite having an analog mechanism - these are usually referred to as flip clocks. An alternative system has been proposed. For example, the "Twelv" clock denotes the current clock using one of the twelve colors, and shows the minute by showing the proportion of a round disk, similar to the lunar phase.

Digital

• Example digital clock

The digital clock displays the numerical representation of time. Two numeric display formats are commonly used in digital clocks:

• 24-hour notation with start hours 00-23;
• 12 hour notation with AM/PM indicator, with clock shown as 12AM, followed by 1 AM-11AM, followed by 12PM, followed by 1 PM-11PM (notation of the most widely used in domestic environment).

Most digital clocks use electronic mechanisms and LCD, LED, or VFD screens; many other display technologies are used as well (cathode ray tubes, nixie tubes, etc.). After reset, battery replacement or power outage, this clock without a spare battery or capacitor starts counting from 12:00, or fixed at 12:00, often with blinking numbers indicating that time needs to be set. The new clock will reset itself by radio or Internet time server set to the national atomic clock. Since the advent of digital clocks in the 1960s, the use of analog clocks has dropped significantly.

A few hours, called 'flip clocks', have a digital display that works mechanically. The figures are painted on a sheet of material mounted like the pages of the book. Once a minute, a page is opened to reveal the next digit. These displays are usually easier to read in bright conditions than LCD or LEDs. Also, they do not come back to 12:00 after power failure. Flip clocks generally do not have an electronic mechanism. Usually, they are driven by an AC-synchronous motor.

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Hours with analog quadrants, with digital components, usually minutes and clocks are displayed analogue and seconds are displayed in digital mode.

Auditory

For comfort, distance, phone or blindness, the auditory clock presents the time as a sound. It is a natural language spoken, (eg "Time twelve thirty-five"), or as a code of hearing (eg The number of successive bell ringing on a clock represents the number of hours like a bell, Big Ben). Most telecommunication companies also provide a talk-time service.

Word

Word clock is a clock that displays the time visually using a sentence. For example: "It's about three o'clock." This clock can be implemented in hardware or software.

Projection

A few hours, usually digital ones, include optical projectors that illuminate enlarged images from time-to-screen display or to surfaces such as ceilings or indoor walls. The numbers are big enough to read easily, without the use of glasses, by people with imperfect eyesight, so the hours are easy to use in their bedroom. Typically, the timer circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection lamp only works when the unit is connected to an A.C supply. Fully portable, battery-powered, flash-like versions are also available.

Tactile

Hearing and projection hours can be used by people who are blind or have limited vision. There are also hours for blind people who have displays that can be read using the sense of touch. Some are similar to normal analog screens, but are built so that the hand can be felt without destroying it. Other types are basically digital, and use devices that use code like Braille to show the digits so they can be felt with the fingertips.

Multi-display

Several hours have multiple views that are driven by a single mechanism, and some have separate mechanisms in one case. Hours in public places often have multiple faces visible from different directions, so the clock can be read from anywhere in the vicinity; all faces show the same time. Other clocks show the current time in some time zones. Watches intended to be carried by travelers often have two screens, one for local time and another for home time, which is useful for making pre-arranged phone calls. Several hours of equations have two screens, which show the average time and other sun time, as indicated by the sun's clock. Several hours have analog and digital displays. Clocks with Braille display usually also have conventional digits that can be read by people who look.

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Destination

Hours at home, offices and many other places; the smaller ones (watches) are carried on the wrist or in the pocket; larger ones are in public places, e.g. a train station or a church. Small hours are often displayed in the corner of computer displays, mobile phones and many MP3 players.

The main purpose of the clock is to show time. Clocks can also have facilities to make a warning signal loudly at any given time, usually to wake the sleep at a predetermined time; they are referred to as alarm clock . Alarms can start with low volume and become louder, or have the facility to shut down for a few minutes then continue. An alarm clock with a visible indicator is sometimes used to show children too young to read the time that bedtime has been completed; they are sometimes called training hours .

The clock mechanism can be used to control the device over time, e.g. central heating system, VCR, or time bomb (see digital counter). Such a mechanism is usually called a timer. The clock mechanism is also used to drive devices such as solar trackers and astronomical telescopes, which must rotate at an accurately controlled speed to counteract Earth's rotation.

Most digital computers rely on internal signals at constant frequency to synchronize processing; this is called a clock signal. (Some research projects are developing CPUs based on asynchronous circuits.) Some equipment, including computers, also retain the time and date to be used as needed; this is called a time-day clock, and is different from the system clock signal, although it may be based on its cycle count.

In Chinese culture, giving hours (????, sÃÆ'²ng zh? Ng) is often taboo, especially for the elderly as the term for this action is homophone with terms for the act of attending other people's funeral (????, sÃÆ'²ngzh? Ng ). A British government official Susan Kramer gave a watch to the Taipei mayor, Ko Wen-je, unaware of such taboos that caused some people to feel professionally embarrassed and apologetic.

It is not recommended to give someone hours or (depending on the region) other watches as a gift. Traditional superstitions consider this a second count for the recipient's death. Another common interpretation of this is the phrase "clocking" (simplified Chinese: ?? ; traditional Chinese: ?/span>) in Chinese pronounced "sÃÆ'²ng zh? ng" in Chinese, which is the homophone of the phrase to "end" or "attend the funeral" (both can be written as ?? (traditional) or ?? (simplified)). The Cantonese regard such gifts as a curse.

These homosexuals work in Mandarin and Cantonese, though in most of China only clocks and large bells, and not watches, are called "zhong ", and watches are usually given as gifts in China.

However, if such a gift is given, the "misfortune" of the prize may be repaid by demanding a small monetary payment so that the recipient buys the hour and thereby excludes the Chinese text "> '?' ("give") phrase expression.

Standard time

For some time the scientific work of the highest accuracy is very important. Also required is a maximum accuracy standard that can be calibrated by working hours. The ideal clock will give time for unlimited accuracy, but this can not be realized. Many physical processes, in particular including several transitions between atomic energy levels, occur at very stable frequencies; such process cycle calculations can provide a very accurate and consistent time - hours working in this way are usually called atomic clocks. Such clocks are usually large, very expensive, require a controlled environment, and are much more accurate than are necessary for most purposes; they are usually used in standard laboratories.

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Source of the article : Wikipedia