The difference between a thermocouple and a PT100 often causes confusion for those who deal with temperature measurement on a daily basis. But, ultimately, which one offers more precision and reliability? Each sensor has its own advantages and limitations, and knowing these points is fundamental to making the right choice.
What is PT100 and Thermocouple?
PT100s and thermocouples are the most widely used temperature sensors in industrial applications. Both have their origins in the early days of electronics and metrology, and are still essential tools for temperature monitoring.
The PT100 is a platinum resistance thermometer, named for its material and its resistance value at 0°C (100 ohms). Resistance increases linearly with temperature, making the sensors accurate and stable.
Thermocouples , on the other hand , consist of two different metal alloys joined at one end, generating an electrical voltage with temperature variations. This voltage can be measured and converted into temperature.
How do PT100 and thermocouples work?
A PT100 sensor operates on the principle that the electrical resistance of platinum increases with temperature. This resistance can be measured and converted to temperature. The PT100 is capable of accurately measuring temperatures over a wide range.
Simply put:
At 0°C, a PT100 sensor has a resistance of 100 ohms. As the temperature increases, the resistance increases linearly, allowing this value to be used to determine temperature. PT100 sensors are often found in industrial applications where accuracy is crucial, such as the chemical and food industries.
A thermocouple is a sensor that measures temperature using the difference in electrical voltage generated by two different metals connected to each other (also known as the Seebeck effect). When the temperature changes, the voltage also varies, making the measurement possible.
There are several types of thermocouples (e.g., Type K, J, T), which differ in the combinations of metals used and in their temperature ranges. They are robust and suitable for extremely high temperatures.
The advantages of thermocouples are undeniable: low cost, small size, robustness, fast response time, and a wide measurement range. They are commonly used in high-temperature applications and harsh environments. However, their accuracy is lower than that of PT100, and their response can be affected by the probe length and connection quality.
See also how to calibrate the PT100.
Differences between Thermocouple and PT100
| Resource | PT100 | Thermocouple |
|---|---|---|
| Measuring Principle | Resistance Changeover (RTD) | Seebeck Effect (Thermoelectric) |
| Material | Platinum | Various combinations of metals |
| Typical temperature ranges | -200 ° C to 850 ° C | -200 ° C to 1800 ° C |
| Precision | Very high (±0,1°C to ±0,5°C) | Varies by type, generally smaller |
| Response time | Slow to medium | Fast |
| Cost | Higher | Lower |
| Calibration | Requires calibration in critical applications | More frequent calibration |
| Application areas | Accurate measurements, laboratories | High temperatures, hostile environments |
| Typical areas of use | Chemical, pharmaceutical, food, steel industry | Metallurgy, glass production |
We've prepared a quick video to explain the differences between a thermocouple and a PT100 . Watch it here:
When to use PT100?
PT100 sensors are ideal for applications requiring high accuracy and stability. Examples include:
– Laboratories: precision is essential in scientific research.
– Food industry: temperature control is important for product quality and safety.
– Pharmaceutical industry: many pharmaceutical processes require strict temperature control.
Another advantage of PT100 sensors is their linearity. This makes them easy to calibrate and allows for accurate temperature measurements without complicated calculations.
When is a thermocouple the best choice?
Thermocouples are ideal for environments where high temperatures and sudden temperature changes occur. They are robust and resistant to vibration and shock, making them a good option for harsh industrial environments.
– Metallurgy: The manufacturing and processing of metals often requires monitoring extremely high temperatures.
– Glass and ceramic production: high temperatures are also required here, and the speed of thermocouples is an advantage.
– Engines and turbines: Temperature monitoring in areas with high vibrations and rapid temperature changes is important.
Read also about the N type of thermocouple.
How accurate are temperature sensors?
One of the main differences between PT100 and thermocouples is accuracy. PT100 sensors offer high accuracy and stability, making them the first choice for precise applications. Thermocouples, on the other hand, are less accurate but offer a fast response time and are suitable for temperatures that a PT100 sensor cannot cover.
PT100 sensors are accurate and stable. They offer very low measurement drift and can remain calibrated for a long time. This is important in processes where temperature plays a critical role.
Thermocouples are less stable and can oscillate for longer periods, requiring regular calibration . However, they are often preferred for extremely high temperatures and rapid temperature measurements.
Installation and handling
PT100 sensors require careful installation due to their delicate structure. The fine wires and sensitive platinum structure must be protected from mechanical stress.
Thermocouples are generally more robust and can be installed directly in hot environments. They are more resistant to vibration and shock, making them more suitable for environments where mechanical stress occurs.
What is the cost difference between a thermocouple and a PT100?
Cost also plays a role in the decision between PT100 and thermocouples. PT100 sensors tend to be more expensive not only because of the use of platinum, but also because of the manufacturing process, which requires high precision to ensure measurement stability and reliability.
Thermocouples, on the other hand, are more affordable, mass-produced, and suitable for applications where cost-benefit is crucial. Therefore, they are often the choice for larger-volume projects or environments that require frequent replacements.
To make the right choices, seek advice and support from a temperature measurement expert. For over three decades, Alutal has mastered the engineering and manufacturing of custom temperature sensors.
Want to know more about the products? Contact Alutal.
