Manual Temperature Compensation
pt = resistivity reading at temperature t
p1 = resistivity reading at temperature t1, 5 °C above temperature t
p2 = resistivity reading at temperature t2, 5 °C below temperature t
pavg = arithmetic average of p1 and p2
p25 = calculated, temperature-compensated resistivity at 25°C
(delta-t) = absolute value of the difference between 25°C and temperature t rounded to the nearest whole number
f = average fractional change in resistivity per °C at temperature t
pavg = (p2 + p1) / 2
f = (p2 - p1) / ((t1 - t2) * pavg)
If t < 25°C, p25 = pt * ((1 - f) ^ (delta-t))
If t > 25°C, p25 = pt * ((1 + f) ^ (delta-t))
For the temperature range of 0 °C to 50°C, the calculated, temperature compensated resistivity at 25 °C (p25) should be within 5% of the resistivity if it had been measured at 25°C.
Temperature Compensation (Marsh and Stokes') Equation
K25 = electrolytic conductivity in µS•cm at 25°C
Kt = electrolytic conductivity in µS•cm at temperature t
t = temperature of measurement in °C
p25 = calculated temperature compensated resistivity at 25°C
K25 =
= ((Kt - A) / B) + 0.05498
p25 = 1 / (K25)
where:
• A = 0.05498 + (2.9326 * (10 ^ (-3)) * (t -25)) + (6.0629 * (10 ^ (-5)) *((t -25)^2)) + (4.2690 * (10 ^ (-7)) * ((t -25) ^ 3))
• B = 1 + (0.02 * (t - 25))
