What is screen refresh rate: 60 Hz, 90 Hz or 120 Hz - pros and cons

SI unit for frequency

This article is about the unit of measurement. For other uses, see Hertz (disambiguation).

"Hz" and "Megahertz" are redirected here. For other uses, see Hz (disambiguation) and Megahertz (disambiguation).

From top to bottom: the indicators blink at frequencies w
= 0.5 Hz, 1.0 Hz and 2.0 Hz, that is, at a frequency of 0.5, 1.0 and 2.0 blinks per second, respectively.
The time between each flash - the period
T - is defined as 1⁄
f
(in reciprocal of
f
), that is, 2, 1 and 0.5 seconds, respectively. (Image edited and adjusted to symmetrical timing pulse using GIMP)

In hertz

(symbol:
Hz
) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second.[1] It is named after Heinrich Rudolf Hertz, the first person to provide conclusive evidence for the existence of electromagnetic waves. Hertz is usually expressed in multiples: kilohertz (103 Hz, kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), terahertz (1012 Hz, THz), petahertz (1015 Hz, pHz), exahertz (1018 Hz , Hz) and zettahertz (1021 Hz, Hz).

Some of the most common uses of the device are described as sine waves and musical tones, especially those used in radio and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics operate. The units are sometimes also used as a representation of energy through the photon energy equation ( E

=
hour
ν), with one hertz equivalent to
an hour
joule.

Definition

Hertz is defined as one cycle per second. The International Committee of Weights and Measures defined the second as "the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom"[2][3] and then adds: "It follows that hyperfine splitting is mainly state of the cesium 133 atom is exactly 9,192,631,770 hertz, ν (hfs Cs) = 9,192,631,770 Hz." The unit unit hertz is 1/time (1/T). Expressed in basic SI units, it is 1/second (1/s). Problems can arise because angle units (cycle or radian) are omitted in the SI system.[4][5][6][7]

In English, "hertz" is also used in the plural.[8] In the SI system, the frequency Hz can be prefixed; Commonly used multiples are kHz (kilohertz, 103 Hz), MHz (megahertz, 106 Hz), GHz (gigahertz, 109 Hz), and THz (terahertz, 1012 Hz). One hertz simply means "one cycle per second" (usually a full cycle is counted); 100 Hz means "one hundred cycles per second", etc. The unit of measurement can be applied to any periodic event - for example, you can say that a clock ticks at 1 Hz, or you can say that the human heart beats at 1.2 Hz.

The occurrence rate of an aperiodic or stochastic event is expressed in a response second

or
reciprocal second
(1/s or s−1) in general or, in the particular case, radioactive decay, in becquerels.[9] Whereas 1 Hz is 1 cycle per second, 1 Bq is 1 aperiodic radionuclide event per second.

Although angular velocity, angular frequency, and all units of hertz have a unit of 1/s, angular velocity and angular frequency are not expressed in hertz,[10] but rather in the corresponding angular unit such as radian per second. Thus, a disk spinning at 60 revolutions per minute (rpm) is said to be spinning at 2π rad/s, or

1 Hz, where the former measures angular velocity and the latter reflects the number of
complete
revolutions per second.
The frequency conversion w
is measured in hertz, and the angular velocity
ω
is measured in radians per second this is
ω = 2 π f {displaystyle omega = 2pi f,} and f = ω 2 π {displaystyle f = {frac {omega} {2pi}}, } .
Hertz is named after Heinrich Hertz. As with every unit named after a person, its symbol begins with an uppercase letter (Hz), but when written fully follows the rules of capitalizing a common noun; those. « hertz

“becomes capitalized at the beginning of a sentence and in headings, but otherwise lowercase.

An excerpt characterizing Hertz (unit of measurement)

“They say that the ball will be very good,” answered the princess, raising her mustache-covered sponge. “All the beautiful women of society will be there.” – Not everything, because you won’t be there; not all,” said Prince Hippolyte, laughing joyfully, and, grabbing the shawl from the footman, even pushed him and began to put it on the princess. Out of awkwardness or deliberately (no one could make out this) he did not lower his arms for a long time when the shawl was already put on, and seemed to be hugging a young woman. She gracefully, but still smiling, pulled away, turned and looked at her husband. Prince Andrei's eyes were closed: he seemed so tired and sleepy. - You are ready? – he asked his wife, looking around her. Prince Hippolyte hastily put on his coat, which, in his new way, was longer than his heels, and, getting tangled in it, ran to the porch after the princess, whom the footman was lifting into the carriage. “Princesse, au revoir, [Princess, goodbye," he shouted, tangling with his tongue as well as with his feet. The princess, picking up her dress, sat down in the darkness of the carriage; her husband was straightening his saber; Prince Ippolit, under the pretext of serving, interfered with everyone. “Excuse me, sir,” Prince Andrei said dryly and unpleasantly in Russian to Prince Ippolit, who was preventing him from passing. “I’m waiting for you, Pierre,” said the same voice of Prince Andrei affectionately and tenderly. The postilion set off, and the carriage rattled its wheels. Prince Hippolyte laughed abruptly, standing on the porch and waiting for the Viscount, whom he promised to take home. “Eh bien, mon cher, votre petite princesse est tres bien, tres bien,” said the Viscount, getting into the carriage with Hippolyte. – Mais très bien. - He kissed the tips of his fingers. - Et tout a fait francaise. [Well, my dear, your little princess is very sweet! Very sweet and perfect Frenchwoman.] Hippolyte snorted and laughed. “Et savez vous que vous etes terrible avec votre petit air innocent,” continued the Viscount. – Je plains le pauvre Mariei, ce petit officier, qui se donne des airs de prince regnant.. [Do you know, you are a terrible person, despite your innocent appearance. I feel sorry for the poor husband, this officer, who poses as a sovereign person.] Hippolyte snorted and said through laughter: “Et vous disiez, que les dames russes ne valaient pas les dames francaises.” Il faut savoir s'y prendre. [And you said that Russian ladies are worse than French ones. You have to be able to take it up.] Pierre, having arrived ahead, like a homely man, went into Prince Andrei’s office and immediately, out of habit, lay down on the sofa, took the first book he came across from the shelf (it was Caesar’s Notes) and began, leaning on his elbow, reading it from middle. -What did you do with m lle Scherer? “She’s going to be completely ill now,” said Prince Andrei, entering the office and rubbing his small, white hands. Pierre turned his whole body so that the sofa creaked, turned his animated face to Prince Andrei, smiled and waved his hand. - No, this abbot is very interesting, but he just doesn’t understand the matter well... In my opinion, eternal peace is possible, but I don’t know how to say it... But not political balance... Prince Andrey was apparently not interested in these abstract conversations. - You can’t, mon cher, [my dear,] say everything you think everywhere. Well, have you finally decided to do something? Will you be a cavalry guard or a diplomat? – asked Prince Andrei after a moment of silence. Pierre sat down on the sofa, tucking his legs under him. – You can imagine, I still don’t know. I don't like either one. - But you have to decide on something? Your father is waiting. From the age of ten, Pierre was sent abroad with his tutor, the abbot, where he stayed until he was twenty. When he returned to Moscow, his father released the abbot and said to the young man: “Now you go to St. Petersburg, look around and choose. I agree to everything. Here is a letter for you to Prince Vasily, and here is money for you. Write about everything, I will help you with everything.” Pierre had been choosing a career for three months and had done nothing. Prince Andrey told him about this choice. Pierre rubbed his forehead. “But he must be a Mason,” he said, meaning the abbot whom he saw at the evening. “All this is nonsense,” Prince Andrei stopped him again, “let’s talk about business.” Were you in the Horse Guards?...

Story

Hertz is named after the German physicist. Heinrich Hertz (1857–1894), who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1930.[11] It was adopted by the General Conference on Weights and Measures (CGPM) ( Conférence générale des poids et mesures

) in 1960, replacing the unit's former name,
cycles per second
(cps), along with associated multipliers, most notably
kilocycles per second
(kc/s) and
megacycles per second
(Ms/s), and sometimes
kilomegacycles per second
(km/s) With).
Period, the term cycles per second
was largely replaced by
the hertz
by the 1970s.
One hobby magazine, Electronics Illustrated
, has stated its intention to stick with the traditional units kc., mc. etc.[12]

Applications

A sine wave with different frequencies

The heartbeat is an example of a non-sinusoidal periodic phenomenon that can be analyzed in terms of frequency. Two cycles are shown.

Vibration

Sound is a traveling longitudinal wave that represents an oscillation of pressure. People perceive the frequency of sound waves as pitch. Each musical note corresponds to a specific frequency, which can be measured in hertz. The baby's ear can perceive frequencies from 20 Hz to 20,000 Hz; The average adult can hear sounds from 20 Hz to 16,000 Hz.[13] The range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from several femtohertz[14] to classified terahertz[15] and beyond.[16]

Electromagnetic radiation

Electromagnetic radiation is often described by its frequency—the number of times the perpendicular electric and magnetic fields oscillate per second—expressed in hertz.

RF exposure is usually measured in kilohertz (kHz), megahertz (MHz) or gigahertz (GHz). Light is electromagnetic radiation, which is even higher in frequency and has frequencies in the range of tens (infrared) to thousands (ultraviolet) terahertz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between the highest commonly used radio frequencies and long-wave infrared light) is often called terahertz radiation. There are even higher frequencies, such as gamma radiation, which can be measured in exahertz (EHz). (For historical reasons, the frequencies of light and higher-frequency electromagnetic radiation are usually defined in terms of their wavelengths, or photons of energy: for more on this and the above frequency ranges, see electromagnetic spectrum.)

Computers

More information on why frequency, including gigahertz (GHz), etc., is a false indicator of speed for computers: The Myth of Megahertz

In computers, most central processing units (CPUs) are designated by their clock speed, expressed in megahertz (106 Hz) or gigahertz (109 Hz). This specification refers to the frequency of the main processor. clock signal. This signal is a square wave, which represents an electrical voltage that periodically switches between low and high logic values. Since the hertz has become the primary unit of measurement adopted by the masses for determining processor performance, many experts have criticized this approach, which they claim is flawed. easy to administer test. Some processors use multiple clock periods to perform a single operation, while others can perform multiple operations in a single cycle.[17] For personal computers, CPU clock speeds ranged from about 1 MHz in the late 1970s (Atari, Commodore, Apple Computers) to 6 GHz in IBM POWER microprocessors.

Different computer buses, such as the front CPU connection bus and the Northbridge, also operate at different frequencies in the megahertz range.

Technical description

To understand what image quality depends on, it’s worth comparing the classes presented in stores:

• liquid crystal (LCD). Affordable and therefore in demand. Fluorescent lighting is used to create the picture, it comes out clear. The storyboard reaches 100 Hz, this allows you to watch movies without any interference and without flickering, this is optimal for vision;
• LED. An improved version of the previous one, LED backlighting has been added. They are distinguished by increased contrast, the final quality depends on the screen diagonal. The Edge LED marking indicates the end distribution of the backlight; it is inferior in quality to the classic arrangement;
• plasma. The class is gradually losing its position. It is a plasma cell with ultraviolet illumination. The advantage is the highest levels of color depth and saturation, but the significant disadvantage is that such devices last no more than 3-4 years. After this period, the panel begins to heat up and the quality drops;
• OLED. This version entered the market just a few years ago. Initially, such TVs were voluminous, which is unusual for the modern consumer. They became much more popular with the release of flat versions. They work without any backlight, but maintain excellent quality and support high video resolutions.

All of the above modifications operate at an average of 100 Hz. The signal arrives at the receiver at a speed of 50 frames per second, then digital processing doubles this parameter. To achieve clarity and smoothness without slowdown, computer graphics uses two main frames and many more intermediate links. Therefore, the refresh index is also important for the monitor.

Multiples of SI

SI, multiples of hertz (Hz)

Higher frequencies than the International System of Units provide prefixes that are believed to occur naturally in the frequencies of quantum mechanical oscillations of high-energy or, equivalently, massive particles, although they are not directly observed and must be inferred from their interactions with others phenomena. By convention, they are usually expressed not in hertz, but in units of equivalent quantum energy, which is proportional to the frequency by a factor. Planck's constant.

How to find out the index?

To find out how many hertz there are in a TV, you can ask this question to a consultant in a store, or read the technical description on the website of a trading platform or equipment manufacturer. This is one of the most important parameters, so finding it among others will not be difficult. If you want to learn about the storyboard of an existing TV, you can look it up in the user manual, on the manufacturer’s website, as well as in the menu of the device itself in the technical data tab. The most reliable option is the manufacturer's website. Each device has a sticker with a personal number; if you specify it, you can get detailed parameters of a specific device.

Notes and links

1. "hertz". (1992). American Heritage Dictionary of the English Language
   (3rd ed.), Boston: Houghton Mifflin.
2. "SI Brochure: Table 3. Associated derived SI units with special names and symbols."
3. "[Regulations] CIPM, 1964 - Atomic and Molecular Frequency Standards" (PDF). SI Brochure Appendix 1.
4. Mohr, J.C.; Phillips, W. D. (2015). "Dimensionless units in SI". Metrology
   .
   52
   (1): 40–47. arXiv:1409.2794. Bibcode:2015Metro..52 … 40M. Doi:10.1088/0026-1394/52/1/40.
5. Mills, I. M. (2016). "In units of radians and cycle for plane angle quantities." Metrology
   .
   53
   (3):991–997. Bibcode:2016Metro..53..991M. Doi:10.1088/0026-1394/53/3/991.
6. “SI units need to be reformed to avoid confusion.” From the editor. Nature
   .
   548
   (7666): 135. August 7, 2011. doi:10.1038/548135b. PMID 28796224.
7. P. R. Bunker; I. M. Mills; Per Jensen (2019). "Planck's constant and its units." J Quant Spectrosc Radiat Transfer
   .
   237
   : 106594. Bibcode:2019JQSRT.23706594B. doi:10.1016/j.jqsrt.2019.106594.
8. NIST Guide to SI Units - 9 Rules and Styles for Writing Unit Names, National Institute of Standards and Technology
9. “(d) Hertz is used only for periodic phenomena, and becquerel (Bq) is used only for random processes in activity related to a radionuclide.” "BIPM - Table 3". BIPM. Retrieved October 24, 2012.
10. "SI Brochure, Section 2.2.2, Paragraph 6." Archived from the original on October 1, 2009.
11. "History of the ICC". Iec.ch. September 15, 1904. Retrieved April 28, 2012.
12. Cartwright, Rufus (March 1967). Beeson, Robert G. (ed.). “Will success spoil Heinrich Hertz?” (PDF). Electronics illustrated
    . Fawcett Publications, Inc., pp. 98–99.
13. Ernst Terhardt (20 February 2000). "Dominant region of the spectrum." Mmk.e-technik.tu-muenchen.de. Archived from the original on April 26, 2012. Retrieved April 28, 2012.
14. "Sound Waves in a Black Hole - Science Mission Directorate." science.nasa.go.
15. Atomic vibrations are usually on the order of tens of terahertz
16. "Sound Waves in a Black Hole - Science Mission Directorate." science.nasa.go.
17. Asaravala, Amit (30 March 2004). "Good dance, Gigahertz." Wired
    . Retrieved April 28, 2012.
18. Unicode Consortium (2019). "Unicode Standard 12.0 - Compatible with CJK Range: 3300–33FF ❱" (PDF). Unicode.org
    . Retrieved May 24, 2022.