Articles » General » Advantages and Disadvantages of Resistance Temperature Detectors (RTDs)

Advantages and Disadvantages of Resistance Temperature Detectors (RTDs)

temperature sensors rtd resistance temperature detector temperature measurement sensors

This article explores the pros and cons of using Resistance Temperature Detectors (RTDs). We’ll delve into their benefits and drawbacks, offering a clear understanding of when and where they excel, and where they might fall short.

Introduction to RTDs

An RTD, or Resistance Temperature Detector, is a type of temperature sensor that relies on the principle that a metal’s electrical resistance changes with temperature. Specifically, RTDs have a positive temperature coefficient, meaning their resistance increases as the temperature goes up.

The typical operating range for an RTD is quite broad, spanning from -250°C to a scorching 1000°C.

RTD curve

Figure 1: A typical voltage versus temperature curve of an RTD.

It’s worth noting the sensitivity and linearity when comparing RTDs to other temperature sensors:

  • Sensitivity Order: Thermistor > RTD > Thermocouple
  • Linearity Order: RTD > Thermocouple > Thermistor

Advantages of RTDs

Let’s look at the reasons why RTDs are often a preferred choice for temperature measurement:

  • High Stability: RTDs are known for their exceptional stability over time. This means they’re less prone to drifting and provide consistent readings.
  • High Accuracy: They offer very accurate temperature measurements, making them ideal for applications that demand precision.
  • Good Linearity: RTDs exhibit a more linear relationship between resistance and temperature compared to thermocouples. This simplifies calibration and signal processing.

Disadvantages of RTDs

While RTDs have many advantages, they also have some limitations:

  • Passive Devices: RTDs are passive devices, meaning they require an external current source to function.
  • Higher Cost: They tend to be more expensive than other types of temperature sensors like thermocouples and thermistors.
  • Self-Heating: When a current passes through the RTD to measure its resistance, the sensor will inevitably heat up a bit. This “self-heating” effect can introduce some error, especially at higher currents.
  • Less Rugged: Compared to thermocouples, RTDs are generally more delicate and less rugged, making them vulnerable in harsh environments.
  • Small Resistance Change: The change in resistance with temperature, while linear, can be quite small. This can require more sensitive measurement circuitry.