Understanding Different Temperature Sensors

We know how to take our own temperature, but how do we measure the heat of other things? That’s where temperature sensors come in! These electronic devices convert temperature into a readable electrical signal, helping us control everything from ovens to industrial machinery.

Thermistor

  • Operating Principle: A resistor that changes resistance significantly in response to temperature changes. Typically made of ceramic or polymer materials.
  • Types:
    • NTC (Negative Temperature Coefficient): Resistance decreases as temperature increases. Most common type.
    • PTC (Positive Temperature Coefficient): Resistance increases as temperature increases.
  • Temperature Range: Limited range, typically -50°C to 150°C
  • Accuracy: Highly accurate within their limited range (around 0.1°C to 0.2°C), but accuracy drops outside that range.
  • Linearity: Highly non-linear output. Requires complex calculations or lookup tables to convert resistance to temperature.
  • Sensitivity: Very sensitive to small temperature changes.
  • Cost: Generally inexpensive.

Thermocouple

  • Operating Principle: Two dissimilar metal wires joined at a junction. A small voltage is generated at the junction proportional to the temperature difference.
  • Types: Many types based on metal combinations (e.g., J-type, K-type, T-type), each with different temperature ranges and characteristics.
  • Temperature Range: Wide range, from -200°C to well over 2000°C, depending on the thermocouple type.
  • Accuracy: Less accurate than RTDs, typically within 1°C to 2°C depending on type.
  • Linearity: Moderately non-linear output over the full range. Requires calibration or correction factors.
  • Sensitivity: Less sensitive than thermistors or RTDs to small temperature changes.
  • Cost: Generally inexpensive but can vary depending on the specific metals used.

RTD (Resistance Temperature Detector)

  • Operating Principle: Changes resistance in a predictable way in response to temperature. Usually made of pure metals like platinum.
  • Types: Most common is the Pt100 (platinum, 100 ohms resistance at 0°C). Other types exist using nickel, copper, etc.
  • Temperature Range: -200°C to about 600°C for platinum RTDs.
  • Accuracy: Highly accurate, often to within 0.1°C or better.
  • Linearity: Excellent linearity over most of their operating range.
  • Sensitivity: Good sensitivity but less than thermistors.
  • Cost: More expensive than thermistors and thermocouples.

Choosing the Right One

The best sensor depends on your application:
  • Thermistor: Best for precise measurements within a limited temperature range.
  • Thermocouple: Best for very wide temperature ranges where moderate accuracy is sufficient.
  • RTD: Best for applications requiring high accuracy and stability over a moderate temperature range.

Why Choose Nexthermal?

Nexthermal is a trusted sensor manufacturer and supplier in North America. Nexthermal can work with you to find the right industry-standard sensor or develop a sensor that is specific to your needs while working to find the best price through our global sourcing capabilities.

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