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Precision Resistance Wire (Ni-Cr-Al) Karmalloy Wire

Manganin wire was the original material used for precision resistance wire. However, among the changes accompanying the miniaturization of modern products, there has been increased
demand for precision resistance materials with high resistivity.
In order to meet such demands, we have developed a Nickel Chromium precision resistance wire,
"Karmalloy wire".

The name of this wire, "Karmalloy", is our registered trademark.

Distinctive features of precision resistance (Ni-Cr-Al) Karmalloy wire

  1. Starting with Nickel Chromium electric heat wire Class 1, we replaced some of the Ni with
    Al and other elements, and thus achieved a precision resistance material with improved
    resistance temperature coefficient and heat electromotive force against copper.
    With the addition of Al, we have succeeded in making volume resistivity 1.2 times greater
    than Nickel Chromium electric heat wire Class 1 and the tensile strength 1.3 times greater.
  2. The secondary temperature coefficient β of Karmalloy wire KMW is very small, - 0.03 × 10-6/ K2,
    and the resistance temperature curve turns out to be almost a straight line within a wide
    temperature range.
    Therefore, the temperature coefficient is set to be the average temperature coefficient between
    23 ~ 53 ˚C, but 1 × 10-6/K, the average temperature coefficient between 0 ~ 100 ˚C, also may
    be adopted for the temperature coefficient.
  3. Electromotive force against copper between 1 ~ 100 ˚C is also small, below + 2 μV/K, and
    exhibits excellent stability over a period of many years.
  4. If this is to be used as a precision resistance material, low temperature heat treatment is
    required to eliminate processing distortions just as in the case of Manganin wire CMW.




    5. Graph 3
    Graph 4


    Table 7  Features of precision resistance (Ni-Cr-Al) Karmalloy wire
    SymbolChemical
    Composition
    %    		Volume resistivity
     μΩ · m     		Mean temperature coefficient
    α X 10‐6/K    		Tensile strength
    MPa    		Elongation
    %
    KMW Cr 19 ~ 21
    Ni 70 ~ 79
    Al others    		1.33 0.05Class AA 10 880 ~ 1200 20 <
    Class A 20
    Class B 


    List of resistance values
    List of insulation types


    Explanation of each symbol

     Kind of insulation
     Insulation tolerance
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