Steinhart-Hart utilities for calculating the relationship between temperature and resistance of thermistors.

steinhart_hart.py

from math import log, exp, sqrt

cbrt = lambda x: x**(1/3)
invert = lambda x: 1/x

def solve_steinhart_hart_eq(R1, T1, R2, T2, R3, T3):

	#Solving the Steinhart-Hart equation
	#Source: https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation#Steinhart%E2%80%93Hart_coefficients

	L1, L2, L3 = map(log, 		(R1, R2, R3))
	Y1, Y2, Y3 = map(invert, 	(T1, T2, T3))

	γ2 = (Y2 - Y1) / (L2 - L1)
	γ3 = (Y3 - Y1) / (L3 - L1)

	C = (γ3 - γ2) / (L3 - L2) / (L1 + L2 + L3)
	B = γ2 - C * (L1**2 + L1*L2 + L2**2)
	A = Y1 - (B + L1**2 * C) * L1

	return A, B, C

def calculate_temperature_for_resistance(A, B, C, R):
	return 1 / (A + B * log(R) + C * log(R) ** 3)

def calculate_resistance_for_temperature(A, B, C, T):
	x = 1/(2*C) * (A - 1/T)
	y = sqrt((B/(3*C))**3 + x**2)
	return exp(cbrt(y - x) - cbrt(y + x))

def c_to_k(T):
	return T + 273.15

def k_to_c(T):
	return T - 273.15