Definitions of Hertz, Kilohertz, etc.

This article defines and compares frequency measurements expressed in Hertz, Kilohertz kHz, Megahertz mHz, Gigahertz gHz, and Terahertz tHz .

Our page top photo illustrates measuring the distance between a hidden electric meter and the head of anyone lying in an adjacent bed.

While the field strength of an EMF around an electric meter or service entry cable falls off very quickly, one can indeed measure a strong field when quite close to the equipment.

Table of Definitions of Kilohertz, Megahertz, Gigahertz, Terahertz

Relation of wavelength to frequency & speed: notice that the shorter the wavelength the higher the frequency.

That's why in our table above as the wavelengths get smaller (notice those negative exponents?) the electromagnetic frequency numbers get larger.

More technically, wavelength is inversely proportional to wave frequency.

Do not confuse wavelength and frequency of an electromagnetic wave with its speed.

All electromagnetic waves move at or close to the speed of light (and do move at the speed of light if measured in a vacuum).

The speed of an electromagnetic wave, expressed in meters per second is equal to wavelength (in meters) x frequency (in oscillations per second or Hertz, abbreviated as Hz).

Photo: cell towers and other electrical devices and antennae in Buenos Aires, Argentina.

• Hertz - Hz is defined as the number of cycles per second of any oscillating or repeating phenomenon, but usually used to define electrical signals, or electrical field frequencies such as those of electromagnetic fields, radio signals, or computer processing clock cycles.
  
  The term Hertz as used in frequency measurement was named for German physicist Heinrich Hertz (1857-1894), who studied electromagnetism, clarified Maxwell's electromagnetic theory of light, and demonstrated the existence of electromagnetic waves.
  
  The term Hertz was established by the International Electrotechnical Commission in 1930.
• Kilohertz - kHz is defined as thousands of cycles per second. Synonyms for kilohertz found in some documents include kc, kilocycle, kilocycles per second.
• Megahertz - mHz is defined as millions of cycles per second - 1000 x more than kilo. See our table below.
• Gigahertz - gHz is defined as billions of cycles per second - 1000 x more than mega, or 1,000,000,000 cycles per second - Microwave towers, UHF and EHF transmission - operate in the 1GHz to 100GHz range.
• Terahertz - tHz is defined as trillions of cycles per second- Wavelengths at frequencies still higher than EHF - GHz are referred to as Terahertz radiation, but are more familiarly understood as infrared light.
  
  Still higher frequencies become light visible to the human eye. One THz is a very high frequency unit of electromagnetic (EM) wave frequency equal to one trillion hertz (10-to-the-12th power Hz)

Our table (below) provides definitions of various frequencies or oscillation rates expressed in kilohertz, megahertz, gigahertz, or terahertz.

The additional Hertz incredibly-high frequencies listed below are not likely to be found in use describing electromagnetic radiation such as those discussed in these articles - these are not in common use, but may be used to describe quantum-mechanical wave functions.

Separately at TABLE of EMR FREQUENCIES we provide a separate listing of the frequency in Hertz of various sources of electromagnetic radiation, ranging from ULF - ultra low frequency sources - through UHF - ultra high frequency electromagnetic radiation sources.

Because the possible effects of electromagnetic fields on humans, other animals, and even materials varies significantly by frequency (and wavelength, distance, and other factors).

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-12-21 by Bill BALHARRY - Why do I sometimes see a capital "K" on KHz instead of kHz

In most cases you quote the Kilohertz abbreviation as kHz, i.e. with a lower case 'k' , however in some Frequency Definitions tables I see the Kilohertz abbreviation as KHz, i.e. with a capital 'K' .

Are both acceptable, or should it really be " kHz " ?

And if it should be with a lower case ' k' , just as you have used lower case for "daHertz" and "hHertz" why, when in all the other definitions you use a capital ?

Reply by InspectApedia Publisher (mod) kHz is correct; electrical engineers are not always careful about capitalization

@Bill BALHARRY,

Most expert sources that we have reviewed abbreviate the term kilohertz as. kHz. But it was very interesting to see a capital k used in a number of perfectly scholarly documents and even in some search engine results.

And indeed over the 70 years of writing about this topic and term neither I nor other electrical engineers I worked with have always been meticulously consistent in Kapitalization.

Since it's not ambiguous in this case, that is, we're not mixing up the meaning of k as "thousands" or kilohertz, kHz has thousands of cycles, we're in luck.

Still, we appreciate consistency as much as the next person. And it's always helpful to know what some of our readers might find troublesome or confusing.

You'll notice that a recent web-search found at least one "major" dictionary, Collins, whose entry wrote the frequency using a capital K.

Properly we should write kilohertz as kHz.

Thanks for your thoughtful and polite discussion.

Daniel

On 2021-03-16 by connie smith : mHz settings for sleep aid devices.

if the mefahertz is 3 for sleep, could you tell me how many seconds between each megahertz like a drum.

Or whatever the sleep pattern is Thank you, Connie

Reply by danjoefriedman (mod)

@connie smith,

One megahertz - one million cycles per second = 1,000,000

so if you have some device set to 3 Mhz that's 3 million cycles every second -

On 2020-12-23by Anonymous - Which frequency measurement is better?

is a yotahertz better than a hertz

Reply by danjoefriedman (mod) - neither

Anon

1 yottahertx = 1 septillion hertz

It's not a better nor worse measurement but would be more useful when expressing very large numbers or cycle rates.

Reader Question: how many zeros in a PetaHertz?

I read in [the article above]

“One petahertz = ten followed by 15 zeros”

I Believe it should be :

One petahertz = one followed by 15 zeros

The same mistake is repeated for the definitions of : Exahertz Zetahertz Yotahertz. - Y. [Annon]

Reply:

Thank you for the question on clarifying how to write the value of various high-frequency measurements such as Petahertz, Exahertz, etc.

The correct formula for one pHz is 1 x 10 to the 15th power

Since 1 x anything is identical to that "anything",

10 to the 1th is 10

10 to the 2d power is 10 x 10 = 100 (1 followed by two zeroes) making you correct

1 x 10 to the 15th is exactly equal to 10 to the 15th which you could write as

1,000,000,000,000,000

or 1 followed by fifteen zeroes - you are quite correct and we have amended our article text to be more accurate.

Reader Question: what's the relationship between Hertz and Milligauss?

Albert Asked: how do Hertz and Milligauss relate to one another when I'm looking at electrical field strength measurement?

Moderato reply:

Albert in the RECOMMENDED ARTICLES

see EMF ELECTROMAGNETIC FIELDS & HUMAN EXPOSURE

Electromagnetic field strength (measured in gauss) falls off as the square of the distance. There is no one fixed number since you need to know the field strength and distance.

About your earlier question, Milligauss relates to Hertz about as "inches" relates to "pounds" - they are different measurement scales.

• Milligauss is a measurement of the strength of an electromagnetic field. Gauss is a unit measurement of electromagnetic strength. The use of the word "milli" means we are expressing the field strength in thousandths of one gauss.
  
  A technical definition of gauss from dictionary.com is pretty specific, and I'll give it below.
  
  But in a practical sense, if we have standards of exposure to an electromagnetic field that are expressed in gauss, typically we just want to compare our exposure measurement (or estimate) with the number in the standard.
  
  As long as we keep the units of measurement the same, gauss, we can make comparisons.
• Hertz measures cycles per second - one Hertz is one cycle per second.
  
  Unlike gauss that is a measurement unit for the strenght of a specific thing (an electromagnetic field), hertz is a generic frequency measurement.

We could be measuring the frequency with which we hear our alarm clock beeping (maybe one Hertz or one beep per second) or we could be measuring the frequency with which we see a chicken cross the road at my sister's house in Georgia: about 0.0003 Hertz - or about one chicken per hour.

They don't cross very often and some of them who try it get run over.

We could say that Linda's road-crossing-chicken-rate was observed to be 0.0003 Hertz. I calculated that as 1 chicken crossing observed in one hour, or 1/3600 seconds = 0.0002777

Formal definition of gauss

gauss: the centimeter-gram-second unit of magnetic induction, equal to the magnetic induction of a magnetic field in which one abcoulomb of charge, moving with a component of velocity perpendicular to the field and equal to one centimeter per second, is acted on by a force of one dyne;

1 maxwell per square centimeter or 10− 4weber per square meter. Symbol: G. - dictionary.com retrieved 2016/03/29

Formal definition of hertz

hertz, the standard unit of frequency in the International System of Units (SI), equal to one cycle per second. Abbreviation: Hz. - op. cit.

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Continue reading at ELECTROMAGNETIC FIELD EMF ELF & RF DETECTION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see DEFINITIONS of HERTZ, KHz MHz GHz THz FAQs - questions and answers about frequency definitions posted originally at the end of this article.

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DEFINITIONS of HERTZ, KHz MHz GHz THz at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ENVIRONMENT

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