Temperature Coefficient of Resistance

Formula

Description

Resistance of most materials changes with temperature. The temperature coefficient α defines the fractional change in resistance per degree Celsius. Metals have positive temperature coefficients (resistance increases with temperature), while semiconductors and carbon have negative coefficients. This first-order linear approximation is valid over moderate temperature ranges. For precision applications over wide temperature ranges, second-order terms become significant. This relationship is exploited in RTD temperature sensors and must be compensated for in precision resistor networks.

Variables

• R — Resistance at operating temperature (Ω)
• Rref — Resistance at reference temperature, usually 25°C (Ω)
• α — Temperature coefficient in ppm/°C
• ΔT — Temperature change from reference (°C)

Practical Notes

Copper TCR is about +3930 ppm/°C, meaning resistance increases 0.39% per degree. Precision resistors have TCR as low as 1-5 ppm/°C. NP0/C0G ceramic capacitors have near-zero TCR. PT100 RTDs use platinum with α = 3850 ppm/°C as a temperature standard. The α value entered here is in ppm/°C and is automatically scaled by 1e-6 internally.