What is the resistance of a Pt100 RTD at 0°C?
A. 10 Ω
B. 500 Ω
C. 100 Ω
D. 1000 Ω
View Answer
Correct Answer: C
Explanation:
A Pt100 RTD is named because it has a resistance of 100 Ω at 0°C.
The term can be broken down as:
- Pt = Platinum
- 100 = 100 Ω resistance at 0°C
According to the IEC 60751 standard, the resistance of a Pt100 RTD changes with temperature. The approximate relationship near 0°C is:
Where:
- RT = Resistance at temperature T
- R₀ = Resistance at 0°C = 100 Ω
- α = 0.00385/°C for a standard platinum RTD
- T = Temperature in °C
At 0°C:
RT = 100 × (1 + 0.00385 × 0)
RT = 100 Ω
Some common Pt100 values are:
- 0°C → 100.0 Ω
- 50°C → 119.4 Ω
- 100°C → 138.5 Ω
- 200°C → 175.9 Ω
Therefore, the resistance of a Pt100 RTD at 0°C is 100 Ω, making Option C the correct answer.