The types of Resistance temperature detectors (RTDs) The devices used in industry may vary depending on the level of precision required, but they all have something in common: they work by changing the electrical resistance in contact with the temperatureUnderstanding how a RTD Understanding how this sensor works and what models exist helps to explain why it is so prevalent in industrial and laboratory processes.
What is thermoresistance?
A resistance thermometer (RTP) is a temperature measuring device used in industrial and laboratory environments, especially in processes that require greater precision and stability. Unlike thermocouples, which operate based on the generation of voltage due to... Seebeck effectIt works by measuring the variation in the electrical resistance of a metal: as the temperature changes, the resistance also changes, and this behavior allows the measured value to be indicated with considerable accuracy.
That's why models like the PT100 They are so common in chemical plants, refineries, power plants, and research areas. Resistance temperature detectors (RTDs) are also the right choice for use in tanks, pipelines, boilers, reactors, climate chambers, and testing equipment. In other words, practically anywhere where temperature needs to be rigorously monitored.
The typical structure of an RTD consists of a very thin wire wound around a ceramic or glass core. Because it is delicate, the sensitive element is usually inserted inside a probe for protection. The operation is simple: by measuring the electrical resistance of the element, the corresponding temperature is determined, since each material has a well-established resistance curve.
For those who wish to learn more, Technical Manager Celso Lopes explains the operation of the PT100 in detail in this video:
What are the types of resistance temperature detectors (RTDs)?
Among the best-known models is the PT100, which gets its name from PLATINUM WIRE (PT), exhibiting 100 ohms at 0°C. It has become a standard in industrial and laboratory processes thanks to its stability, adequate response time, and reliability in measurements. Other models, such as the PT500 and PT1000, are also used according to the required sensitivity and range.
Resistance temperature detectors (RTDs) can be classified according to the material of the sensing element, the element's construction, and the type of connection. Platinum RTDs, such as... Pt100, Pt200, Pt500 and Pt1000Platinum is the most widely used material in the world. It offers excellent linearity, stability, and repeatability, ensuring highly reliable measurements. Therefore, it is the standard adopted by IEC 60751.
Nickel RTDs emerge as a more economical alternative, although they have a shorter operating range, generally up to 300°C, and lower stability when compared to platinum.
There are also copper RTDs, which offer good linearity and reduced cost. They are quite common in HVAC systems. However, copper oxidizes easily, which limits its use in more aggressive industrial environments.
See our table and compare the performance of different types of resistance thermometers:
Here is the updated table. including PT500 and PT5000, maintaining the same simple, direct and organized pattern:
| RTD type | Material | Approximate Temperature Range | Specifications: |
|---|---|---|---|
| PT100 | Platinum | -200 ° C to + 600 ° C | The most widely used in the industry; high precision and stability. |
| PT500 | Platinum | -200 ° C to + 600 ° C | More sensitive than the PT100; a good alternative when greater resistive variation is desired. |
| PT1000 | Platinum | -200 ° C to + 600 ° C | High durability; less susceptible to noise; ideal for long cables. |
| PT5000 | Platinum | -200 ° C to + 600 ° C | Very high resistance; extremely stable; reduces interference and noise effects. |
| Ni100 | Nickel | -60 ° C to + 180 ° C | Good sensitivity, but limited use due to the narrower frequency range. |
| Cu10 / Cu50 | Copper | -200 ° C to + 260 ° C | Good linearity, but less resistant to oxidation. |
| RTD Thin Film | Platinum (thin film) | -70 ° C to + 500 ° C | Quick response, compact size, and good value for money. |
| RTD Wire-Wound | Platinum (coiled wire) | -200 ° C to + 850 ° C | High precision, ideal for critical applications. |
| Ceramic RTD | Platinum | -200 ° C to + 600 ° C | Stable in high temperatures and harsh environments. |
| Glass RTD | Platinum | -100 ° C to + 450 ° C | Good stability and resistance to moisture. |
If you want, I can turn this into running text, version SEO, version UOLor in the format explaining each model in detail.
What changes between the different types of resistance thermometers?
The number of wires is one of the factors that most influences accuracy. In a 2-wire RTD, the cable resistance adds to the sensor value, which can generate considerable error; therefore, it only works well with short cables or measurements that don't require high precision. The 3-wire model is the industry standard because it compensates for some of the cable resistance and offers good accuracy without increasing the system cost. The 4-wire RTD delivers the best possible performance: it virtually eliminates all error caused by cables and is used in critical measurements, laboratories, and calibrations.
The physical construction of the element also determines performance and durability. Thin-film RTDs use a thin layer of platinum over ceramic, ensuring fast response and lower cost. Wire-wound RTDs, in turn, offer superior precision and long-term stability, performing better in temperature extremes. Mineral-insulated (MI) RTDs combine mechanical strength, vibration tolerance, and the ability to operate in harsh environments, characteristics that justify their presence in heavy-duty industrial sectors.
Also read about How to calibrate a PT100
Discover the PT100 temperature sensor from Alutal.
Alutal is one of the most traditional companies in the country when it comes to temperature measurement, especially with thermocouples and thermoresistors. With over three decades in the market, the manufacturer has built a solid reputation by delivering precise, durable sensors that meet the demands of sectors where failure is not an option.
The company's structure helps explain why its sensors stand out. Alutal maintains its own calibration laboratory, certified and recognized in the country, which allows it to test each batch of sensors before they reach the customer. This process gives the PT100 an important advantage: real metrological traceability, something essential for those who work with critical processes or need to follow specific technical standards. It's the kind of detail that can go unnoticed, but makes a big difference in practice.
The Alutal PT100 follows exactly this line. It is a sensor designed to offer stable readings, precision even with rapid temperature variations, and mechanical resistance to operate in challenging environments, from production lines to outdoor areas exposed to vibration, humidity, and sudden heat changes. It's the type of equipment that keeps up with the heavy demands of industry without sacrificing performance.
Request a quote now and ensure accurate, stable, and reliable measurements for your business.
FAQ
Both PT100 and PT1000 are made of platinum and follow the same principle. The difference lies in their resistance: the PT100 exhibits 100 Ω at 0°C, while the PT1000 exhibits 1000 Ω. In many applications they can be used interchangeably, but the PT1000 tends to offer better performance over long distances, as its higher resistance reduces cable impact.
The main difference is the operating principle. While RTDs measure changes in resistance, thermocouples measure the voltage generated by the junction of two different metals. RTDs are more precise, stable, and linear, but have a smaller temperature range. Thermocouples can operate at very high temperatures and have a faster response, but offer less precision.
