Thermistor and RTD interface
Thermistor and RTD interface with explicit circuit assumptions and worked equations.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
NTC beta: 1/T = 1/T0 + ln(R/R0)/β
Steinhart–Hart: 1/T = A + B ln R + C(ln R)^3
IEC RTD: R/R0 = 1 + AT + BT² [+ C(T−100)T³ below 0 °C]
Ratiometric conversion: code = round[(2^N−1) R/(Rfixed+R)]
Assumptions
- Temperatures in thermistor equations are kelvin. Self-heating result applies to separate constant-current excitation; divider excitation dissipates a different power. RTD values use published IEC platinum coefficients, without lead resistance or sensor tolerance. Three-point NTC fit is empirical and should not be extrapolated outside calibrated temperatures.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Sensor model
- beta
- Solve from
- temperature
- Temperature
- 25 °C
- Measured resistance
- 10000 Ω
- NTC reference resistance
- 10000 Ω
- NTC reference temperature
- 25 °C
- NTC beta
- 3950 K
- Fit temperatures °C
- 0, 25, 85
- Fit resistances Ω
- 32650, 10000, 1070 Ω
- Constant excitation current
- 0.0001 A
- Dissipation constant
- 0.001 W/K
- Divider/ADC reference voltage
- 3.3 V
- Divider top resistor
- 10000 Ω
- ADC resolution
- 12 bits
Results
- Sensor resistance
- 10000 Ω
- Sensor temperature
- 25 °C
- Ratiometric divider output
- 1.65 V
- ADC code
- 2048
- Constant-current self-heating estimate
- 0.1 K
- NTC linearising parallel resistor
- 7376.77 Ω