Thermocouples have an important position in many types of industries, since they help one measure and then control temperature perfectly. Among them, the commonly used sensors include thermocouples and RTD temperature sensors. Even though the main purpose that these two sensors satisfy is the same, they present an enormous design, performance difference, and hence in applications also. This article looks into these differences between the two sensors such as Thermocouples and RTD sensors.
What is a Thermocouple?
A thermocouple is actually a sensor produced when two dissimilar metals are joined at one end. It produces a voltage proportional to the temperature difference if exposed to heat or cold. Thermocouples then convert these voltages into temperature readings.
Thermocouples come in some very basic forms and types, ranging from probes, to bare-wire thermocouples, to infrared thermocouples, and even transition joint probes. Each of them, however, serves more or less different applications.
They are widely used due to their wide range of temperatures and durability. Some thermocouples can measure temperatures up to 2500°C, which is ideal for extreme environments.
What is an RTD Temperature Sensor?
An RTD, or Resistance Temperature Detector, is a temperature sensor that relies on the principle that a material’s resistance changes with temperature. Among these RTDs, platinum (Pt100) is one of the most common ones and made from platinum. The Pt100 is said to be precise, to repeat, and very stable.
RTD elements consist of a thin wire coiled around a ceramic or glass core. This delicate element is normally put in a protective sheath to avoid breakage. RTDs are highly used in laboratories and industrial processes for their precise and consistent temperature readings.
Thermocouple vs. RTD Temperature Sensor: Key Comparisons
- Temperature Range
- Thermocouples: Ideal for high-temperature applications, with some models capable of measuring up to 2500°C.
- RTD Sensors: Generally up to 400°C, though advanced RTD designs can measure a little higher.
- Cost
- Thermocouples: Generally cheaper because of the simpler manufacturing process.
- RTD Sensors: More expensive than thermocouples, which can be two to three times as expensive for similar applications. Installation costs for RTDs are lower since they use inexpensive copper wires.
- Sensitivity
- Thermocouples: They respond quickly to temperature changes, and the fastest is the exposed-tip thermocouple.
- RTD Sensors: Slightly slower in response time compared to thermocouples, but thin-film RTD designs have improved this aspect significantly.
- Accuracy
- RTD Sensors: Offer higher accuracy, typically within ±0.1°C.
- Thermocouples: Generally less accurate, with most models having an accuracy of ±1°C. Some specialized thermocouples can match RTD accuracy.
- Linearity
- RTD Sensors: Exhibit a near-linear relationship between temperature and resistance, making them easier to calibrate.
- Thermocouples: Have a non-linear “S”-shaped curve that can complicate calibration.
- Stability
- RTD Sensors: Stable, consistent readings. Long-term data should be consistently within a predetermined acceptable range in order to give minimum drift.
- Thermocouples: Inclined toward chemical changes oxidation drift, relatively unstable long-time measurements.
Choosing the Right Sensor for Your Needs
Depending on an application, pick one between them as per individual requirement: Whether a thermocouple or a temperature sensor called an RTD
For high-temperature applications, cost-sensitive projects, and fast response times, thermocouples are the best. They are usually used in industrial furnaces, engines, and other extreme conditions.
RTD Sensors are perfect for applications that require accuracy, stability, and repeatability. They are commonly used in laboratories, food processing, and medical equipment.
Conclusion
Thermocouples and RTD temperature sensors both have their advantages and disadvantages. Thermocouples are less expensive and can operate at high temperatures, while RTDs provide precise and stable measurements across a broad temperature range. The sensor type to be chosen would depend on your application’s temperature range, accuracy, and budget.
At Metalogic Sensor, we make available high-quality RTD temperature sensors for industrial and laboratory applications. Explore our range to find the perfect solution to meet your temperature measurement needs!