Frequency
Updated 2026-10-27
Data records
- Expressed in SI base units, the hertz equals the reciprocal of the second. Value: s-1.
- Frequency is the number of cycles of a periodic quantity completed in unit time; for an alternating voltage or current it is the reciprocal of the period of one cycle.
- Frequency is read by multimeters with a frequency function, by power quality analyzers that log it continuously against the nominal system value, and by frequency counters, which count the cycles of a signal over a gated time interval.
- The power frequency is the nominal frequency at which an alternating-current power system is operated. Two nominal values predominate worldwide, the choice between them is regional, and a test instrument is specified for one or both of them.
- In the NIST Guide to the SI, the hertz, symbol Hz, is the SI coherent derived unit of frequency, and a note to its table entry states that the hertz is used only for periodic phenomena. Value: Hz.
Elsewhere in the family
- Frequency more on this entry on Power Quality Reference
- Power frequency variation related entry on Power Quality Reference
- IEEE Recommended Practice for Monitoring Electric Power Quality related entry on Power Quality Reference
Sources
- Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
- NIST SP 811, NIST Guide to the SI, Chapter 4: The Two Classes of SI Units and the SI Prefixes, web page updated 2025-08-18 edition, NIST. Cited: clause Table 3; clause Table 3, note d. Held as: Government work. Publisher page
Changelog (11 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-27 | created (qty.frequency.base-units) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.frequency.base-units) | |
| 2026-10-27 | created (qty.frequency.definition) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.frequency.definition) | |
| 2026-10-27 | created (qty.frequency.measured-by) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.frequency.measured-by) | |
| 2026-10-27 | created (qty.frequency.power-frequency) | |
| 2026-10-27 | revised (qty.frequency.power-frequency) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.frequency.power-frequency) | |
| 2026-10-27 | created (qty.frequency.unit) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.frequency.unit) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Frequency." Test Instrument Reference. 2026-10-27. https://www.testinstrumentreference.com/quantities/frequency/.
Test Instrument Reference, Frequency (Oct. 27, 2026), https://www.testinstrumentreference.com/quantities/frequency/.
@misc{etr-quantities-frequency,
title = {Frequency},
howpublished = {\url{https://www.testinstrumentreference.com/quantities/frequency/}},
organization = {Test Instrument Reference},
publisher = {Test Instrument Reference},
year = {2026},
note = {last substantive change 2026-10-27}
}{{cite web |title=Frequency |website=Test Instrument Reference |publisher=Test Instrument Reference |url=https://www.testinstrumentreference.com/quantities/frequency/ |date=2026-10-27 |access-date=}}