NTC Thermistor Steinhart-Hart Equation (3-Constant)

1/T = A + B ln(R) + C (ln R)^3, T in kelvin, A/B/C off the datasheet or a 3-point calibration (C is tiny, ~1e-7). Holds to ~+/-0.01-0.02 C across a wide span (-50 to 150 C) where the two-point beta drifts to +/-0.2-1 C. A 10 kohm NTC with A 1.1253e-3, B 2.3471e-4, C 8.566e-8 reads 25.0 C at 10 kohm, ~2 C at 29 kohm, ~48 C at 3.9 kohm (negative-coefficient: R falls as T rises). Distinct from a positive-coefficient platinum RTD. The datasheet R-T curve, tolerance, and self-heating govern.

1/T = A + B ln(R) + C (ln R)^3, T in kelvin; T = 1/(A + B ln R + C (ln R)^3); output in C and F. A, B, C from the datasheet or a 3-point calibration.

NTC thermistor 3-constant Steinhart-Hart resistance-temperature equation, by name (Steinhart & Hart, Deep-Sea Research, 1968); the sensor datasheet R-T curve and tolerance govern.

The Steinhart-Hart equation is public; A, B, and C are the three datasheet coefficients (or are fit from three known resistance-temperature points), and R is the field reading.

Estimate. AHJ and licensed professional govern.

Field names used by the API: resistance_ohms, coeff_a, coeff_b, coeff_c, temperature_c, temperature_f

• Steinhart-Hart equation 1/T = A + B ln(R) + C (ln R)^3, kelvin; NTC, so R falls as T risesSteinhart & Hart (1968) / NTC datasheet
• Coefficients A, B, C from the datasheet or a 3-point calibration; C ~ 1e-7 (drop it for a 2-constant form)thermistor datasheet
• Accuracy ~+/-0.01-0.02 C over a wide span vs +/-0.2-1 C for the two-point beta equationthermistor practice