Clock
A clock is an instrument capable of measuring, maintaining and indicating time in conventional units (hours, minutes or seconds). Fundamentally, it allows knowing the current time, although it can have other functions, such as measuring the duration of an event or activating a signal at a certain specific time.
Watches have been used since ancient times and as their manufacturing technology has evolved, new models have appeared with greater precision, better features and presentation, and lower manufacturing cost. It is one of the most popular instruments, since practically many people have one or several watches, mainly wristwatches, so that in many homes there may be several watches, many household appliances incorporate them in the form of digital watches and in each computer there is a clock.
The watch, in addition to its practical function, has become an object of jewelry, a symbol of distinction and appreciation.
The highest precision achieved so far is that of the last atomic clock developed by the National Bureau of Standards (NIST) of the United States, the NIST-F1, launched in 1999, it is so accurate that it has a margin of error of only one second every 45 million years.
History
Several species of clocks were known in ancient times. Vitruvius speaks of the water clock or hourglass, the air clock, the sun clock and other species that are unknown.
The Egyptians measured the movements of the Sun with the gnomon. The illustrious astronomer used the same means for his observations. Hourglasses and sundials were invented in Egypt in the days of the Ptolemies; The hourglasses were later perfected by Scipio Nasica or according to others by Ctesibius (a disciple of Roman orators who used them to measure the duration of his speeches.)
It is believed that the large clocks with weights and wheels were invented in the West by the Benedictine monk Gerberto (pope, with the name of Silvestre II, towards the end of the 10th century) although they were already known in the Byzantine Empire some time before. Dante, in The Divine Comedy, canto X of El paraíso, before the year 1321AD, tells about mechanical clocks with an alarm function, "whose wheels move one to the other, and rush the one in front until it is heard. tin tin with notes so sweet", like something normal.
According to other sources, the first clock that history talks about built on mechanical principles is that of Richard of Wallingford, abbot of San Albano, who lived in England around 1326, apparently the invention of Gerbert (later Silvester II) was nothing more than a sundial. The second is the one that Santiago Dondis ordered to be built in Padua around 1344 and in which, according to what they say, the course of the sun and the planets was seen. The third was the one in the Louvre in Paris, ordered to be brought from Germany by King Charles V of France. The direct ancestor of these instruments could be the complex Antikythera mechanism, dated between 150 B.C. C. and 100 B.C. C.
In Spain, the oldest news of the installation of a tower clock dates back to 1378, when the conditions established between the chapter of the cathedral of Valencia and Juan Alemany, master clockmaker from Germany, were collected in a document. to make a large dial clock to place it in the old bell tower. Among the mechanical clocks considered the oldest in the country is the "seny de les hores" clock that was installed in the Barcelona cathedral in 1393; that of the bell tower of the church of San Miguel in the town of Cuéllar (Segovia) that was fixed in the year 1395 and finally in the cathedral of Seville another in 1396, whose inauguration took place on July 22, 1400 in the presence of the King Henry III of Castile.
The first person who imagined building pocket watches was Pedro Bell from Nuremberg; their appearance earned them the name "Nuremberg eggs". In 1647, Christiaan Huygens applied the pendulum to tower or wall clocks, the discovery of which is due to Galileo. The same physicist applied the spiral spring to pocket watches in 1665. In 1647, the Genevan Gruet, resident in London, applied to the clock the steel chain that serves to transmit the movement of the drum to the cone, replacing the vihuela strings used until then. Two years later repeater watches were invented.
There are a wide variety of different types of watches. Currently, personal watches are mostly mechanical and electronic, whether analog or digital, they work with a small electric battery that by means of impulses rotates the needles (analog watches) or marks the numbers (digital watches).
There are a large number of mechanical watches for personal (wrist or pocket) or general use (wall and hall clocks). Mechanical watches are estimated and valued more than electronic ones despite their lower accuracy and higher price; since they are considered by experts as mechanical works of art.
Today there are a large number of watch companies, manufacturers of mechanical watches, both personal and fixed, countries such as Germany, Switzerland, Japan, China, the United Kingdom, the United States and Russia, are home to important companies in the sector. In the analogue format there is a fixed scale and two needles that rotate at a constant speed; the shortest and widest hand indicates the hours, and takes twelve hours to complete a complete turn, the thinnest and longest hand, the minute hand, indicates the minutes and takes one hour to complete one complete turn of the clock face. There may be a third hand on the same axis or with a different axis that indicates the seconds and takes one minute to complete a revolution.
On digital clocks, there are two groups of two digits each, separated by a colon (:), the first two indicate time in 24-hour format 0 to 23 or in 12-hour format from 1 to 12; the second group of digits indicates the minutes in a range from 0 to 59, in some cases there may be a third group of two digits that indicates the seconds in a range from 0 to 59 seconds.
Types of watches
Sundials
The apparent position of the Sun in the sky moves throughout each day, reflecting the rotation of the Earth. Shadows cast by stationary objects move accordingly, so their positions can be used to indicate the time of day. A sundial shows time by showing the position of a shadow on a (usually) flat surface, which has markings corresponding to the hours. Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in antiquity. With knowledge of latitude, a well-constructed sundial can measure local solar time with reasonable accuracy, to within a minute or two. Sundials continued to be used to monitor clock performance until the 1830s, with the use of the telegraph and the train to standardize time and time zones between cities.
Wristwatches
At first, they were only worn by women, until World War I (1914-1918), when they became popular among men in the trenches.
Wristwatches all come with two adjustable straps that are attached to either wrist for reading. They are of analog and digital type. Although the face of most of them is generally round, there are also square, hexagonal and even pentagonal faces.
In analog (continuously variable) watches, the time is indicated on the face by two or three hands: a short one for the hour, a long one for the minutes and, optionally, a third long hand that marks the seconds. In digital watches (discrete variable) the time is read directly in numbers on the screen. There are also mixed watches, that is, analog and digital on the same face.
Calendar watches are mechanical or digital watches that mark the current year, month, day of the week, hour, minute, and even seconds.
Chronograph
A chronograph is a watch function that allows short times to be counted on demand. Although it is always confused with a stopwatch, they are different things. A watch can be certified as a chronograph if it includes the function, but a chronograph cannot be considered a chronometer. They are analogue, usually featuring two small additional dials (one for the hours and one for the minutes) that are added to the central dial. with the hand indicating the seconds. Among the three, they indicate the number of revolutions of the central needle. Usually at least one of the needles can be stopped and restarted. It allows to measure speeds, and in the past, doctors used it to control the patient's pulse.
Stopwatch
The chronometer is a watch whose accuracy has been checked and certified by an institute or precision control center. The word chronometer is a neologism of Greek etymology: Χρόνος Cronos is the Titan of time, μετρον -metron is today a suffix meaning measuring device.
Normally, the terms stopwatch and chronograph are often confused. Currently, the Swiss Official Chronometer Control (COSC) is the body that certifies most of the chronometers manufactured. For at least two weeks, in different positions and temperatures, the behavior and differences obtained with respect to the criteria and maximum deviations allowed are tested. Watches certified as chronometers are normally accompanied by a chronometry certificate and a mention on the dial. As reported by the COSC on its website, between 1.6 and 1.8 million watches a year are certified as chronometers, which represents 6% of Swiss watches exported in the same period.
Clocks of towers and bell towers
Before personal wrist and pocket watches were invented, very large clocks with complicated and heavy mechanisms were invented that were placed on top of the towers and bell towers of towns and cities so that citizens would know the time of day. day. These clocks were connected to a large and sonorous bell and it is the one that indicated with a peculiar touch the hours and quarter hours when they were fulfilled. Over the years, clocks of this type have become very famous, such as the Great Clock of Westminster located in the Elizabeth Tower of the British Parliament Palace or the one located in the Puerta del Sol from Madrid.
Living room clocks
Clocks have figured for centuries as important pieces in the furnishing of living rooms, for which they were built with various decorative shapes. Apart from the hourglass, which has been used since the Greek and Roman civilizations to measure short and preset periods, clocks were used in very small numbers until the end of the 13th century or the middle of the 14th century, when the motor was invented. spring or royal spring, spreading the use of the clock-furniture in the 16th century.
Some very curious specimens from this period are preserved in the Louvre, Berlin and Vienna Museums, which have the external shape of a building crowned with a small dome where the bell or bell of the hours is located.
The pocket watch
Pocket watches were invented in France in the mid-15th century, shortly after the hairspring was applied to watchmaking. At first they were cylindrical in shape, varying a lot and with strange caprices, and from the beginning of the XVI century they were built in Nuremberg in profusion and in an ovoid shape, from which the name Nuremberg eggs derives, believed to have been invented in this German and Italian city.
Atomic Clock
An atomic clock is a type of clock that uses a normal atomic resonance frequency to power its counter. Early atomic clocks took their reference from a maser. National standards agencies maintain an accuracy of 10-9 seconds per day and an accuracy equal to the frequency of the radio transmitter that pumps the maser.
Atomic clocks maintain a continuous and stable time scale, International Atomic Time (IAT). For daily use another chronological scale is disseminated: Coordinated Universal Time (UTC). UTC is derived from TAI, but is synchronized using leap seconds with Universal Time (UT1), which is based on the day-night transition based on astronomical observations.
Other types
Other types of watches according to their shape or use are:
- Clock Atmos
- Binary watch
- Water watch or clepsydra
- Chess watch
- Sand clock
- Pocket watch
- Quartz clock
- Cuckoo or cuckoo clock
- Diamond watch
- Fire watch
- Mass watch
- Pendulum watch
- Sunglasses
- Steam watch
- Sail watch
- Alarm clock
- Digital watch
- Electronic watch
- Smart watch
- Foliot watch
- Japanese watch
- Metronome
- Taximeter
Watch Parts
A watch with a traditional dial usually has hands for the hour, minute (for the minutes), and second (for the seconds) and hour (for the hour) hands. In addition, you can additionally have an alarm clock or calendar.
Operation of electronic clocks
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| Screen of a digital clock with seconds. |
An electronic clock is a clock in which the time base is electronic or electromechanical, as is the frequency division. The accuracy of the clock depends on the time base, which can consist of an oscillator or an adapter that, from a reference, generates a periodic signal.
The frequency divider is a digital circuit formed by a succession of counters until a frequency of 1 Hz is obtained, which allows seconds to be displayed. If you want to show tenths, the division stops when you reach 10 Hz. This frequency goes to the presentation module, which can be electronic or mechanical, where other dividers separate the seconds, minutes and hours to present them using some type of of screen.
How mechanical watches work
Mechanical watches lack in most cases electronic components; These types of watches have a mechanical system generally made of metal, where the driving force necessary to start the machinery is provided by a motor spring or by means of weights connected by chains or cables.
In popular culture it is common to refer to the charging of the motor spring as "winding", however this term is misleading, and is only applicable to weight watches, where a cylinder inside is literally wound. of the clock so that in this way the descent of the weight that gives life to it continues. Inside a motor spring there is a tempered steel band or tape that, when wound, generates a torsion force used by the watch to move the mechanism, either the march or the striking. By means of a gear train the force is reduced and the speed increased, ending in a toothed wheel in a special way, called an escape wheel, which connects with a piece called an anchor. This piece is in charge of converting the rotary movement of the gears into a lateral displacement from left to right that is transmitted to a flywheel or a pendulum to provide them with enough energy to oscillate. It is the contact between these two pieces, escape wheel and anchor that produces the famous tic-tac. Finally, the pendulum or the balance wheel mark the passage of time and are known as the regulatory body. The watch uses its constant oscillations or alternations to determine the passage of time: the more precise the mechanism, the fewer variations there will be in the periodicity of the oscillations.
It should be noted that, although wristwatches, which use balance wheels as a regulating body, have achieved surprising levels of accuracy; The pendulum and its regular periodic oscillation continue to be the most accurate timekeeping standard or regulating organ in mechanical clocks.
Normally the number of gears or wheels that a mechanical watch has is a direct consequence of the estimated time in which the spring or the weight will provide enough energy to work; Thus, if a mechanical watch, for example an alarm clock, is built to store 24 hours of running time, the number of wheels will generally be five, from the spring gear to the escape wheel; On the other hand, if it is a wall clock, where the power reserve is designed to last 192 hours (eight days), then an extra wheel will be added just after the motor spring in order to increase the speed of the mechanism. exhaust in relation to the speed of rotation of the motor spring, thus expanding the operating autonomy of the mechanism, although in these cases more powerful springs are required to compensate for the loss of force caused by the increase in the gear ratio; finally, the time is always displayed in analog format, by means of hands, which use the rotation of internal gears, usually the first wheel for 1-day watches, and the second wheel for 8-day watches, to convert the movement of the gear train, controlled by the escapement system, in understandable indications for people, who read the time by looking at the position of the hands in front of a fixed hour scale on the face of the clock.
It should be noted that the minute hand in the mechanical watch, unlike the hour hand, does not have an independent gear train that adjusts the relationship to mark the time, it is fixed to the wheel that usually meshes with the motor spring, Said wheel has an axis that protrudes, in front of the machinery, and which is in fact the axis known as "cannon", where the minute hand is connected, therefore this wheel rotates exactly once every 60 minutes, the hour cannon performs a speed reduction, using a small gear train located on the front of the watch just between the minute and hour hands, the ratio between the two would then be 1/12, where for every turn of the hour hand, the minute hand has Due to turning 12 times, this mechanism is also found in all electronic watches with analog reading.
Time base
The type of time base used is so important that it often gives the clock type its name. The most common are:
- Net pattern. It has no oscillator and uses as a reference the 50 Hz (or 60 Hz) of the network. It is the simplest, but it is quite accurate in the medium term, as the alterations in the network frequency are usually compensated throughout the day. It has two important drawbacks:
- It needs a “clean” signal, for which it is usually filtered before applied to the counters.
- It needs the network, which does not allow its portable use and also, in front of a light cut, loses the time. There are models that include an oscillator and batteries or batteries, so that the oscillator and counters continue to work during the cut, so the time is not lost.
- Emissory pattern. The time base comes to be some kind of PLL, hooked with one of the time stations. They are set in hours alone and change to winter or summer hours autonomously. Its inconvenience is that it needs the time signal, so that in “dark” areas it has no greater advantages.
- Diamond watch. The oscillator is controlled by an intercalated fingerboard on the feeding loop. It has already fallen into disuse, but at the time they were high, and Bulova, for example, had wristwatches.
- Quartz clock. It replaces the fingerboard with a quartz resonator, usually at 32768 Hz, because it is exact power of two, which simplifies the frequency divider. Due to its stability and economy it has shifted all other types of watch in the usual applications.
- Atomic watch (Ammonia, cesium, etc.) It is based on the inclusion of a cavity with molecules of the proper substance in the food loop, so that the resonance of any of its atoms is excited.
The mechanical clock is based on a pusher that can be 1 Hz or a submultiple. In general, this push button was a mechanical escapement mechanism in which the energy stored in a spring was released in a constant and slow manner. The ticking sound of the watch corresponds to this escapement system, which is responsible for generating the time base of the watch and provides movement to the second hand; Both the minute hand and the hour hand are moved by gear trains that transform the ratio of the second hand to 1/60 for the minute hand and 1/60 for the hour hand (see image).
A digital clock consists of an oscillator, usually quartz, which by means of a frequency divider, similar to gear trains, generates the signals of 1 Hz, 1/60 Hz and 1/3600 Hz for the second hand, minute hand and time respectively. In this case, the different electrical pulses pass to 3 cascading counters that correspond to the seconds, minutes and hours respectively on the screen. These counters are coupled to allow the necessary sequence of counting and signaling from one counter to another, namely 0 to 59 for seconds and minutes and 0 to 24 or 1 to 12 for hours, depending on the particular design or configuration. in models that allow both.
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