Editing Resistor (section)

==Standards==

===Production resistors===
Resistor characteristics are quantified and reported using various national standards. In the US, MIL-STD-202<ref>{{cite web |url=http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-STD-202/std202.pdf |title=Test method standard: electronic and electrical component parts |publisher=Department of Defense |url-status=dead |archive-url=https://web.archive.org/web/20150209025640/http://www.dscc.dla.mil/downloads/milspec/docs/mil-std-202/std202.pdf |archive-date=2015-02-09 }}</ref> contains the relevant test methods to which other standards refer.

There are various standards specifying properties of resistors for use in equipment:
* [[IEC 60062]] (IEC 62) / [[DIN 40825]] / [[BS 1852]] / [[IS 8186]] / [[JIS C 5062]] etc. ([[Resistor color code]], [[RKM code]], date code)
* [[EIA RS-279]] / [[DIN 41429]] (Resistor color code)
* [[IEC 60063]] (IEC 63) / [[JIS C 5063]] <!-- / UNE 20531 --> (Standard E series values)
* MIL-PRF-26
* MIL-PRF-39007 (Fixed power, established reliability)
* MIL-PRF-55342 (Surface-mount thick and thin film)
* MIL-PRF-914
* MIL-R-11 Standard Canceled
* MIL-R-39017 (Fixed, General Purpose, Established Reliability)
* MIL-PRF-32159 (zero ohm jumpers)
* UL 1412 (fusing and temperature limited resistors)<ref>[https://web.archive.org/web/20080210020811/http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=1412.html Fusing Resistors and Temperature-Limited Resistors for Radio- and Television- Type Appliances UL 1412]. ulstandardsinfonet.ul.com</ref>

There are other United States military procurement MIL-R- standards.

===Resistance standards===
The [[primary standard]] for resistance, the "mercury ohm" was initially defined in 1884 in as a column of mercury 106.3&nbsp;cm long and {{nowrap|1 square millimeter}} in cross-section, at {{nowrap|0 degrees Celsius}}. Difficulties in precisely measuring the physical constants to replicate this standard result in variations of as much as 30&nbsp;ppm. From 1900 the mercury ohm was replaced with a precision machined plate of [[manganin]].<ref>[http://nvl.nist.gov/pub/nistpubs/sp958-lide/063-065.pdf Stability of Double-Walled Manganin Resistors] {{Webarchive|url=https://web.archive.org/web/20061006125243/http://nvl.nist.gov/pub/nistpubs/sp958-lide/063-065.pdf |date=2006-10-06 }}. NIST.gov</ref> Since 1990 the international resistance standard has been based on the [[quantum Hall effect|quantized Hall effect]] discovered by [[Klaus von Klitzing]], for which he won the Nobel Prize in Physics in 1985.<ref>Klaus von Klitzing [http://nobelprize.org/nobel_prizes/physics/laureates/1985/klitzing-lecture.pdf The Quantized Hall Effect]. Nobel lecture, December 9, 1985. nobelprize.org</ref>

Resistors of extremely high precision are manufactured for [[calibration]] and [[laboratory]] use. They may have four terminals, using one pair to carry an operating current and the other pair to measure the voltage drop; this eliminates errors caused by voltage drops across the lead resistances, because no charge flows through voltage sensing leads. It is important in small value resistors (100–0.0001&nbsp;ohm) where lead resistance is significant or even comparable with respect to resistance standard value.<ref>{{cite web |url=http://www.tinsley.co.uk/products/standard-resistors/4737b.htm |title=Standard Resistance Unit Type 4737B |publisher=Tinsley.co.uk |access-date=2008-09-22 |url-status=dead |archive-url=https://web.archive.org/web/20080821154924/http://www.tinsley.co.uk/products/standard-resistors/4737b.htm |archive-date=2008-08-21 }}</ref>