How the Pt100 conversion works
A Pt100 has a nominal resistance of 100 Ω at 0 °C; a Pt1000 has 1000 Ω. The calculator uses the standard 0.00385 platinum characteristic coefficients and numerically solves the inverse resistance-to-temperature conversion across −200 to 850 °C.
Why a linear shortcut is not enough
The familiar approximation of about 0.385 Ω/°C for a Pt100 is useful near 0 °C, but the relationship is not perfectly linear across the complete range. Use the full relationship or the transmitter/input module’s certified conversion when calibration accuracy matters.
Two-wire lead error
In a two-wire circuit, both copper leads are in series with the sensor, so the input interprets their resistance as additional temperature. A Pt1000 is proportionally less sensitive to the same absolute lead resistance, while a properly implemented three- or four-wire measurement compensates much of the lead effect.
This is not a calibration certificate
The result is an ideal reference. Sensor tolerance class, self-heating, immersion depth, thermal gradients, transmitter error, input accuracy, lead mismatch and calibration uncertainty remain separate contributors.