How to Make the Right Choice Between Pt100/Pt1000 Platinum Resistors and NTC Thermistors?

Temperature measurement is a critical aspect of various industrial applications, particularly in the low to medium temperature range. Two of the most commonly used temperature sensing elements are Pt100/Pt1000 platinum resistors and NTC (Negative Temperature Coefficient) thermistors. While both have their place in the industry, understanding their differences can help you make an informed decision based on your specific needs.

Overview of Pt100/Pt1000 and NTC Thermistors

Pt100/Pt1000 Platinum Resistors

Temperature Coefficient: Positive Temperature Coefficient (PTC)

Applications: Widely used in process control industries.

Advantages:

• Conforms to international standards (IEC 751 / DIN EN 60 751).

• Excellent long-term stability and temperature cycling performance.

• Wide temperature range (up to 500°C with thin-film technology).

• High measurement accuracy and linearity across a broad temperature range.

NTC Thermistors

Temperature Coefficient: Negative Temperature Coefficient (NTC)

Applications: Commonly used in machine manufacturing due to cost advantages.

Advantages:

• High measurement accuracy and linearity, but only within a limited temperature range (typically up to 150°C).

• Lower cost, especially for large-volume orders.

Key Considerations When Choosing a Temperature Sensor

1. Standardization and Interchangeability

Pt100/Pt1000: These sensors are standardized, ensuring interchangeability and consistency across different manufacturers.

NTC Thermistors: Lack standardization due to variations in materials and manufacturing processes, leading to poorer interchangeability.

2. Temperature Range and Accuracy

Pt100/Pt1000: Offers a broader temperature range and maintains high accuracy and linearity across this range.

NTC Thermistors: Provide high accuracy but only within a narrower temperature range.

3. Long-Term Stability

Pt100/Pt1000: Superior long-term stability and performance over repeated temperature cycles.

NTC Thermistors: Generally stable but may not match the long-term reliability of platinum resistors.

4. Cost Considerations

NTC Thermistors: More cost-effective for large-volume orders.

Pt100/Pt1000: The cost difference has decreased due to advancements in thin-film technology, making them a viable option for medium-volume orders.

5. Impact of Lead Resistance

Pt100/Pt1000: Lead resistance can affect measurement accuracy, especially in two-wire configurations. For example, a 0.22 mm² copper cable has a resistance of 0.162 Ω/m, which can introduce an error of 0.42°C/m for Pt100 and 0.04°C/m for Pt1000.

NTC Thermistors: Lead resistance has a lesser impact at lower temperatures but can disproportionately affect measurements at higher temperatures.

Summary and Recommendations

When selecting a temperature sensor, consider the following:

For Large-Volume Orders: NTC thermistors are cost-effective and suitable for applications with limited temperature ranges.

For Medium to Small-Volume Orders: Pt100 or Pt1000 platinum resistors are recommended. The Pt1000, in particular, offers a balance between cost and performance, providing higher accuracy and better overall performance without a significant cost increase.

Comparative Table of Temperature Sensors (Note: ++ Excellent, + Good, – Poor)

Both Pt100/Pt1000 platinum resistors and NTC thermistors have their unique advantages and limitations. Your choice will depend on factors such as temperature range, required accuracy, long-term stability, and cost considerations. For applications requiring high precision and reliability over a wide temperature range, Pt100/Pt1000 sensors are the preferred choice. However, for cost-sensitive, large-volume applications with limited temperature ranges, NTC thermistors remain a viable option.

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