2.3.3 Resistors and Heating
- Page ID
- 2765
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Basic requirements for resistors (still one of the most numerous component in circuits) are:
- Large region of R values (= device resistance in Ω) 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
- Ta, Ta 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:
- FeNiCr, FeNiAl alloys.
- Pt, W, Ta, Mo - 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.
- Overview of resistivity and temperature range for some materials
- Maximum temperatures for some materials