What is the temperature coefficient (alpha) typically used for Pt100 RTDs?

What is the temperature coefficient (alpha) typically used for Pt100 RTDs?

• A. Approximately 0.01 per °C.
• B. Approximately 0.00385 per °C.
• C. Approximately 0.0001 per °C.
• D. Approximately 0.01 per °F.

Answer: (B)

Alpha is the fractional change in resistance per degree of temperature. For platinum resistance thermometers like the Pt100, the standard value used is about 0.00385 per degree Celsius. This means every 1 °C rise increases the resistance by roughly 0.385% of its value at 0 °C. For a Pt100 (100 Ω at 0 °C), a 1 °C increase adds about 0.385 Ω, giving around 100.385 Ω; at 100 °C, the resistance is about 138.5 Ω if you use the linear approximation. The other options don’t fit because they imply either too large or too small a change per degree, or they use a per-degree-Fahrenheit unit, which isn’t the standard for Pt100 RTDs.

Alpha is the fractional change in resistance per degree of temperature. For platinum resistance thermometers like the Pt100, the standard value used is about 0.00385 per degree Celsius. This means every 1 °C rise increases the resistance by roughly 0.385% of its value at 0 °C. For a Pt100 (100 Ω at 0 °C), a 1 °C increase adds about 0.385 Ω, giving around 100.385 Ω; at 100 °C, the resistance is about 138.5 Ω if you use the linear approximation. The other options don’t fit because they imply either too large or too small a change per degree, or they use a per-degree-Fahrenheit unit, which isn’t the standard for Pt100 RTDs.