Resistive Element
Precision electrical resistors fabricated from cold-rolled alloy sheets bonded to ceramic substrates deliver low temperature coefficients of resistance. A bulk metal foil resistor provides tight resistance tolerances down to five thousandths of a percent under stable laboratory temperatures. Mechanical strain compensation within the bonded structure cancels thermal expansion effects across working temperature bands.
The strain balance breaks down when operating voltages induce self-heating above maximum rated power limits.
Strain Coupling
Differential thermal expansion between the metal sheet and the alumina carrier creates mechanical stress during power application. In bulk metal foil devices, compressive stress alters crystal lattice spacing to counteract the inherent positive temperature coefficient of the bare alloy. This mechanical compensation maintains resistance stability across extended operating spans.
Thermal Sensitivity
Power dissipation generates internal heat that shifts the resistive equilibrium away from nominal values. A bulk metal foil element limits thermal drift to less than one part per million per degree Celsius through matched expansion properties.
Qualification Limit
Long-term shelf-life testing verifies resistance stability under continuous electrical load over thousands of hours. The bulk metal foil construction resists moisture absorption and oxidation under hermetic glass encapsulation. Environmental exposure past maximum storage temperatures causes permanent lattice relaxation.
