Resistance Temperature Drift Calculator

Modern online calculator for the temperature dependence of resistors

Calculation

Temperature dependence

The resistance of all materials is temperature dependent. Calculate here the resistance value at a specific temperature using the temperature coefficient.

1/K
Temperature coefficient table
°C
Positive values = heating, Negative values = cooling
Result
Resistance change ΔR:
New resistance:

Good to know

Temperature coefficient

The temperature coefficient α indicates the resistance change for a resistance of 1 ohm when heated by one kelvin (K) or degree Celsius.

Material types
PTC (Positive):
• Copper: +0.00393
• Aluminum: +0.004
• Silver: +0.0038
NTC (Negative):
• Carbon: -0.00005
• Constantan: ±0.00004
• Manganin: ±0.00002
Basic formulas
\[\Delta R = \alpha \times \Delta T \times R_k\] \[R_w = R_k + \Delta R\]
ΔR = resistance change, R_w = new resistance
Validity range

The formula is valid only up to about ΔT = 200K. For larger temperature changes, nonlinear effects become important.

Description of temperature drift

The resistance of all materials is more or less temperature dependent. The temperature drift of a resistor describes how much the resistance value changes when the temperature changes.

Material behavior

PTC (Positive Temperature Coefficient):

Behavior: Resistance increases with temperature

Example: Copper conducts better when cold

Application: Overcurrent protection, inrush current limiting

NTC (Negative Temperature Coefficient):

Behavior: Resistance decreases with temperature

Example: Carbon conducts better when warm

Application: Temperature measurement, inrush current limiting

Formulas for resistance change

Resistance change:
\[\Delta R = \alpha \times \Delta T \times R_k\]

Where:

  • \(\alpha\) = Temperature coefficient (1/K)
  • \(\Delta T\) = Temperature change (K or °C)
  • \(R_k\) = Resistance at 20°C (Ω)
New resistance:
\[R_w = R_k + \Delta R\]
\[R_w = R_k(1 + \alpha \times \Delta T)\]

Where:

  • \(R_w\) = Resistance at warm temperature (Ω)
  • Both formulas are equivalent

Temperature coefficients of important materials

Material Temperature coefficient α (1/K) Type Application
Copper 99.9% +0.00393 PTC Wires, coils
Aluminum 99.9% +0.004 PTC High voltage lines
Silver +0.0038 PTC Contacts, RF technology
Carbon -0.00005 NTC Resistors (obsolete)
Constantan -0.00008 to +0.00004 Stable Precision resistors
Manganin ±0.00002 Stable Measuring resistors

Practical examples

Example 1: Copper wire

Given: Copper wire with 100Ω at 20°C, heating by 50°C

\[\Delta R = 0.00393 \times 50 \times 100 = 19.65\text{ Ω}\] \[R_w = 100 + 19.65 = 119.65\text{ Ω}\]

The resistance increases by almost 20%!

Example 2: Precision resistor

Given: Manganin resistor 1kΩ at 20°C, heating by 30°C

\[\Delta R = 0.00002 \times 30 \times 1000 = 0.6\text{ Ω}\] \[R_w = 1000 + 0.6 = 1000.6\text{ Ω}\]

Only 0.06% change - very stable!

Important notes
  • Temperature coefficients can vary depending on material purity
  • For some metals, resistance is 0Ω at absolute zero (-273.16°C) (superconductors)
  • The linear formula is valid only up to about ΔT = 200K
  • For larger temperature changes, quadratic terms become important
  • Precision resistors use special alloys for minimal temperature drift
Applications
Temperature measurement:
• Pt100/Pt1000 sensors
• NTC thermistors
• Resistance thermometers
Protection circuits:
• PTC fuses
• Overcurrent protection
• Inrush current limiting
Compensation:
• Temperature compensation
• Precision meters
• Reference resistors

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