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2.3.3 Resistors and Heating

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    2765
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    Resistors

    Basic requirements for resistors (still one of the most numerous component in circuits) are:

    • Large region of R values (= device resistance in ) within one production technology.
    • Small (ideally vanishing) temperature coefficient .
    • Minimal noise.
    • Small dependence of ρ on production parameters (good repeatability).
    • No Ageing.
    • Small thermoelectrical coefficients to Cu (you want a resistor, not a thermoelement).

    Materials of choice include

    • TaTa based alloys, and in particular "Constantan" (55% Cu, 44% Ni, 1% Mn), a resistor material with an especially small temperature coefficient αρ, but a large thermoelectric coefficient).
    • Strange mixtures of conductors and insulators including "Cermet" (short for Ceramics - Metals), e.g. Cr - SiO2.

    Details and data in the (future) link.

    Heating

    Basic requirements for heating elements are:

    • High melting point.
    • Chemical stability at high temperatures and in potentially corrosive environments.
    • Mechanical strength at high temperatures.

    The choice of a materials depends significantly on the range of temperatures envisioned. We have:

    • FeNiCrFeNiAl alloys.
    • PtWTaMo - stable elements with a high melting point.
    • MoSi2 Among more industrial applications also used as heaters in dish washers - this is very aggressive environment!
    • Graphite (up to 3000 K in non-oxidizing gas).

    Some details and data can be found in the links.