Work out rtd resistance to temperature instantly with clear inputs, formula shown and shareable results.
The Callendar-Van Dusen equation R = R0(1 + At + Bt squared) inverts to a quadratic for temperature above 0 degrees C. A Pt100 changes only 0.385 ohm per degree, so one ohm of lead resistance is a 2.6 degree error — which is why three- and four-wire connections exist.
Callendar-Van Dusen
R = R0 (1 + A t + B t^2), A = 3.9083e-3, B = -5.775e-7 for a 385 ppm platinum RTD
To cancel lead resistance. Two-wire connection adds the cable resistance directly to the measurement, which at 0.385 ohm per degree is a large error.
Pt1000 has ten times the sensitivity, so lead and noise errors matter ten times less. It is the better choice unless legacy instrumentation dictates Pt100.