Why is platinum preferred for RTD?
A. Low thermal conductivity
B. High melting point
C. Low manufacturing cost
D. Stable characteristics
View Answer
Answer: D
Explanation:
Platinum is preferred for RTDs because of its highly stable characteristics over time and temperature.
A good RTD material must provide a predictable and repeatable relationship between resistance and temperature. Platinum excels in this area, making it the industry standard for temperature measurement.
Advantages of Platinum RTDs
Excellent long-term stability
High measurement accuracy
Good repeatability
Nearly linear resistance-temperature relationship
Wide operating temperature range
Excellent corrosion and oxidation resistance
Why Stability Matters
Platinum RTDs maintain their calibration and measurement accuracy for many years, even under harsh industrial conditions. This reduces measurement drift and minimizes recalibration requirements.
For example:
- Pt100 at 0°C = 100 Ω
- Pt100 at 100°C ≈ 138.5 Ω
These values remain highly consistent over the life of the sensor.
Why the Other Options Are Incorrect
Low thermal conductivity
- Not the primary reason platinum is used.
High melting point
- Platinum does have a high melting point, but this is not the main reason for its selection in RTDs.
Low manufacturing cost
- Platinum is relatively expensive compared to other metals.
Stable characteristics
- This is the key reason platinum is the preferred RTD material.
Because of its excellent stability, accuracy, and repeatability, Option D (Stable characteristics) is the correct answer.