RTD (Resistance Temperature Detector) temperature, understanding the basics is crucial for achieving accuracy and reliability. RTDs work on the principle that the resistance of a metal, such as platinum, increases predictably with temperature. This predictable change allows RTDs to deliver precise temperature readings, making them essential in industrial applications where exact temperature control is critical.

Platinum is commonly used in RTDs because of its stable and repeatable resistance-temperature relationship. For a newly joined engineer, grasping this concept is vital, as it enables the effective utilization of RTDs across various temperature measurement scenarios. Mastering the basics of RTD functionality will enhance your ability to implement and troubleshoot these sensors in real-world applications, ensuring accurate and reliable temperature monitoring.
A common way to use the PT100 is to add a transmiter, that converts the resistance into a 4-20mA signal. Such current loop is stable over long cable lengths

For Pt100 RTD and temperature coefficient of resistance, α = 0.003850 where, α = (R100 – R0)/(100 × R0); A = 3.90830 × 10 - 3; B = -5.77500 × 10 - 7; C= 4.18301 × 10 - 12 for -200°C ≤ T ≤ 0°C; C= 0 for 0°C ≤ T ≤ 850°C.

The PT100 is a resistance temperature detector (RTD), which can measure temperatures from -200 degrees to a maximum of 850 degrees Celsius, but is not usually used to measure temperatures over 200 degrees. This sensor produces a resistance for a given surrounding temperature.

This equation helps convert the resistance measured by the RTD into a temperature value. The formula is: R(T) = R0(1 + A × T + B × T² – 100 × C × T³ + C × T⁴), where R(T) is the RTD resistance at temperature T (°C), and R0 is the RTD resistance at 0°C.