Which statement about Pt100 RTD characteristics is correct?

Which statement about Pt100 RTD characteristics is correct?

• A. The temperature coefficient alpha is approximately 0.00385 per °C, and the nominal resistance at 0 °C is 100 Ω.
• B. Alpha is approximately 0.0100 per °C, and 50 Ω at 0°C.
• C. Alpha is approximately 0.0001 per °C, and 200 Ω at 0°C.
• D. Alpha is approximately 0.005 per °C, and 120 Ω at 0°C.

Answer: (A)

Pt100 RTDs are defined by two key numbers: the resistance at 0 °C and the temperature coefficient that describes how resistance changes with temperature. For a Pt100, the resistance at 0 °C is 100 ohms, and the temperature coefficient is about 0.00385 per degree Celsius. This means the resistance increases with temperature, roughly by 0.385 ohms for every degree rise in temperature. The practical relation R ≈ R0(1 + αΔT) captures this linear behavior near ordinary temperatures, so at 100 °C the resistance is about 100 × (1 + 0.00385×100) ≈ 138.5 Ω. That combination—100 Ω at 0 °C and α ≈ 0.00385 /°C—is the standard Pt100 characteristic, which is why that statement is correct. The other options propose different base resistances or much larger or smaller α values, which do not align with how Pt100 sensors are defined.

Pt100 RTDs are defined by two key numbers: the resistance at 0 °C and the temperature coefficient that describes how resistance changes with temperature. For a Pt100, the resistance at 0 °C is 100 ohms, and the temperature coefficient is about 0.00385 per degree Celsius. This means the resistance increases with temperature, roughly by 0.385 ohms for every degree rise in temperature. The practical relation R ≈ R0(1 + αΔT) captures this linear behavior near ordinary temperatures, so at 100 °C the resistance is about 100 × (1 + 0.00385×100) ≈ 138.5 Ω. That combination—100 Ω at 0 °C and α ≈ 0.00385 /°C—is the standard Pt100 characteristic, which is why that statement is correct. The other options propose different base resistances or much larger or smaller α values, which do not align with how Pt100 sensors are defined.