Resistance Temperature Detector (RTD) Questions – 1

Calculate Temperature from the RTD

Question :

Suppose you need to determine the temperature of a fluid inside a pipe. Installed in this pipe is a 2-wire 100 Ω RTD inside a thermowell, not connected to a transmitter or any other circuit. You happen to have a multimeter with you to measure resistance at the RTD leads.

Touching the two test leads of your multimeter together, you measure 0.3 Ω. Then, connecting those same leads to the RTD’s wires, you measure 184.6 Ω. You do not happen to have an RTD table with you, but you do carry a calculator.

Calculate the approximate temperature of the fluid in this pipe, assuming the most common α value for 100 Ω RTDs.

Answer :

The α value is most likely 0.00385, resulting in a calculated temperature of 218.96 ^oC or 426.13 ^oF.