Editing Resistor (section)

===Metal foil resistor===
[[File:Metal foil resistor.png|thumb|Metal foil resistor]]

In 1960, [[Felix Zandman]] and Sidney J. Stein<ref name=zandman64>{{cite journal |title=A New Precision Film Resistor Exhibiting Bulk Properties |year=1964 |doi=10.1109/TCP.1964.1135008|last1=Zandman |first1=F. |last2=Stein |first2=S. |journal=IEEE Transactions on Component Parts |volume=11 |issue=2 |pages=107–119 }}</ref> presented a development of resistor film of very high stability.

The primary resistance element of a foil resistor is a chromium nickel alloy foil several [[micrometre|micrometers]] thick. Chromium nickel alloys are characterized by having a large electrical resistance (about 58 times that of copper), a small temperature coefficient and high resistance to oxidation. Examples are Chromel A and Nichrome V, whose typical composition is 80 Ni and 20 Cr, with a melting point of 1420&nbsp;°C. When iron is added, the chromium nickel alloy becomes more ductile. The Nichrome and Chromel C are examples of an alloy containing iron. The composition typical of Nichrome is 60 Ni, 12 Cr, 26 Fe, 2 Mn and Chromel C, 64 Ni, 11 Cr, Fe 25. The melting temperature of these alloys are 1350&nbsp;°C and 1390&nbsp;°C, respectively.<ref>''Procedures in Experimental Physics'', John Strong, p. 546.</ref>{{full citation needed|date=December 2021}}

Since their introduction in the 1960s, foil resistors have had the best precision and stability of any resistor available. One of the important parameters of stability is the temperature coefficient of resistance (TCR). The TCR of foil resistors is extremely low, and has been further improved over the years. One range of ultra-precision foil resistors offers a TCR of 0.14&nbsp;ppm/°C, tolerance ±0.005%, long-term stability (1 year) 25&nbsp;ppm, (3 years) 50&nbsp;ppm (further improved 5-fold by hermetic sealing), stability under load (2000 hours) 0.03%, thermal EMF 0.1&nbsp;μV/°C, noise −42&nbsp;dB, voltage coefficient 0.1&nbsp;ppm/V, inductance 0.08&nbsp;μH, capacitance 0.5&nbsp;pF.<ref>{{cite web|url=http://www.alpha-elec.co.jp/e_machine.html |title=Alpha Electronics Corp. Metal Foil Resistors |publisher=Alpha-elec.co.jp |access-date=2008-09-22}}</ref>

The thermal stability of this type of resistor also has to do with the opposing effects of the metal's electrical resistance increasing with temperature, and being reduced by thermal expansion leading to an increase in thickness of the foil, whose other dimensions are constrained by a ceramic substrate.{{citation needed|date=July 2018}}