What kind of clocks are there?

What kind of clocks are there?

A clock is an instrument for measuring and indicating time. The diameter of the movement is generally greater than 50 mm and the thickness is generally greater than 12 mm. It is usually used in a certain position. Some modern small clocks also use the movement of the watch to install the case of the clock.

The development of clock has experienced thousands of years (see the history of clock technology). With the continuous expansion of the scope of use, modern clocks have more and more functions and types. Generally, it can be classified according to vibration principle, energy and structural characteristics, and main uses, and often named by several classification methods.

Principle classification

Most of the colored lacquer inlaid copper drum type clock use periodic vibration process to measure time. According to the principle of producing periodic vibration, clocks can be divided into four categories: ① mechanical vibration clocks with lower frequency, such as pendulum type mechanical clocks, cycloidal hairspring type mechanical clocks, etc. Its vibration frequency is usually several Hertz or even less than one hertz, the daily difference (see clock daily difference) is 10-120 seconds per day, and the daily difference of high-precision astronomical pendulum clock is a few thousandths of a second per day. ② Ordinary electromagnetic vibration clock with higher frequency, such as tuning fork clock, transistor clock, AC synchronous clock, etc. The vibration frequency is usually within 1000Hz, and the daily difference is 2 ~ 20s / day. ③ Quartz oscillatory clocks with higher frequency, such as various quartz electronic clocks. The oscillation frequency is usually within 5MHz (32768Hz, 4194304hz, etc.), and the daily difference is generally within 0.2s/day. The high-precision quartz electronic clock has been used for decades, and the error is no more than 1s. ④ Atomic oscillator clock with higher frequency, such as cesium atomic clock. The frequency is 9192631770hz (the second of atomic time is the duration of 9192631770 cycles of transition radiation between two hyperfine energy levels of cesium atom ground state in zero magnetic field). Its accuracy and stability are very high, and the relative frequency stability can reach 10-13. In view of this, in 1967, the International Committee of weights and measures decided to take the atomic time of cesium atomic clock as the time measurement standard.

According to the characteristics of energy and structure, it can be divided into mechanical clock, electro-mechanical clock, AC synchronous clock, electronic clock, photoelectric clock, temperature difference clock, etc. ① Mechanical clock: driven by mechanical energy, usually with heavy hammer or spring as energy storage elements, each basic component of the clock is composed of mechanical parts (see mechanical clock mechanism). There are pendulum clock, alarm clock, travel clock, etc. ② Electromechanical clock: driven by electric energy (alternating current or battery), its basic components include both mechanical parts and electronic components. The vibration system adopts the combination of mechanical vibration and electromagnetic circuit. There are transistor clock, pendulum clock, tuning fork clock, etc. The travel time precision of this kind of clock is higher than that of ordinary mechanical clock, and it is more convenient to use. However, the structure of quartz electronic clock is complex, and it has been rarely developed after it was put into the market. ③ AC synchronous clock: the vibration system is actually the generator of the power plant. The movement of the clock is mainly a synchronous motor, which converts electrical energy into mechanical energy and drives the pointer system to operate. The travel time accuracy of the clock is restricted by the frequency stability of the AC power supply of the power supply system. ④ Electronic clock: driven by electric energy (AC or battery), its basic components are generally composed of electronic components (pointer system also adopts mechanical transmission). Quartz electronic clock is the most widely used electronic clock. Due to the use of quartz oscillator with stable oscillation frequency and corresponding integrated circuit, quartz electronic clock has obvious advantages over other kinds of clocks, including high travel time accuracy, good stability, easy use, low power consumption, long travel time, small volume, multi-function, low system cost, etc. There are two ways for quartz electronic clock to indicate time: pointer type and digital display. Some clocks have two ways (see quartz electronic clock structure). ⑤ Photoelectric clock: light (including natural light and electric light) is used as energy, and silicon photocell is used to convert light energy into electric energy, which is input into storage battery to supply electric energy for the clock. The charging voltage and current of silicon photocell can be designed according to the needs. Although this kind of clock avoids the trouble of battery replacement, it increases the manufacturing cost. ⑥ Temperature difference clock: it uses the energy produced by a certain substance due to the rise and fall of air temperature as the energy source. This kind of clock is to put a kind of material with large expansion coefficient (such as chloroethane, c2h5cl) into a retractable sealed box, and one end of the box is linked with the upper bar mechanism. When the air temperature changes and causes the sealing box to expand and contract, the sealing box can be automatically loaded. The movement of a clock is a special mechanical movement. The cost of this kind of clock is high and the production capacity is small.

Use classification

It can be divided into living clock and special clock (or technical clock). Different movement structures can be made into clocks for the same purpose, while the basic movement of the same structure can be made into clocks for different purposes as long as a few parts are added or changed. ① Life clock: the clock that people use to time in their daily life. Including travel clock, stand-alone clock, alarm clock, seat clock (see pendulum clock), twist pendulum clock, wall clock (also known as wall clock), floor clock, tower clock, master clock, world clock, radio clock (used in public places, can receive the time signal sent by transmitter) and flower bed clock. ② Special clock: clock with professional timing function. Used in industry, transportation, astronomy, sports, military and other departments. It includes cycle clock (which can indicate the error value of 50 Hz frequency of alternating current emitted by power plant), work and rest clock, attendance clock, time switch clock, product clock (accumulated working time), car clock, ship clock, nautical astronomical clock, tank clock, submarine clock, sports clock (see sports clock), observatory precision pendulum clock, cesium atomic clock, rubidium atomic clock and hydrogen atomic clock, etc.

In order to expand the use of the clock, additional mechanisms can be added to various types of basic movements to increase functions. These additional organizations include single calendar organization, double calendar organization, three calendar (date, week, month) organization, various activities, various time reporting devices, etc