RTDs

A Resistance Temperature Detector (RTD) is a precision temperature sensor designed for high accuracy and long-term stability. Using pure platinum, RTDs measure temperature by detecting changes in electrical resistance as heat varies. Known for their superior reliability and repeatability, RTD sensors are widely used in industries such as pharmaceuticals, energy, food processing, and aerospace, where precise temperature monitoring is critical. Compared to thermocouples, RTDs offer greater accuracy and stability over time, making them ideal for process control, laboratory and calibration applications. Available in wire-wound and thin-film designs, RTD probes can be customised for different environments and integrated into industrial systems. Their durability, consistency, and ability to perform across a wide temperature range make RTD temperature sensors the trusted choice for demanding applications.

The main difference between a Pt100 and a Pt1000 temperature sensor lies in their resistance values. A Pt100 has a resistance of 100 ohms at 0 °C, while a Pt1000 has 1,000 ohms at the same reference point. Both use platinum as the sensing element, ensuring high accuracy and stability, but their resistance levels affect performance in different applications. Pt100 sensors are widely used in industrial environments for process control and calibration due to their robustness and standardization. Pt1000 sensors, with higher resistance, are less sensitive to lead wire resistance and electrical noise, making them well-suited for precision measurement in smaller devices or longer cable runs. Choosing between Pt100 and Pt1000 depends on installation requirements, accuracy needs, and environmental conditions. Both provide reliable, repeatable temperature monitoring across critical industries.

The difference between 2-wire, 3-wire, and 4-wire RTD temperature sensors lies in how they compensate for lead wire resistance, which affects measurement accuracy. A 2-wire RTD is the simplest configuration, where lead resistance adds directly to the sensor reading—suitable only for short cable runs or less critical applications. A 3-wire RTD adds a third lead to help offset lead resistance, making it the most common choice for industrial process control where good accuracy and cost efficiency are required. A 4-wire RTD offers the highest accuracy by fully eliminating the effect of lead resistance, even over long cable lengths, and is preferred in laboratories, calibration systems, and precision applications. Selecting between 2, 3, and 4-wire RTDs depends on installation distance, accuracy requirements, and budget, with each configuration offering a balance between simplicity, cost, and performance.

RTD temperature sensors are classified by accuracy standards defined in IEC 60751. The most common classes are Class A, Class B, and their tighter variants (e.g., 1/3 DIN, 1/10 DIN). Class A RTDs provide higher accuracy, while Class B is more cost-effective for general applications. For even greater precision, 1/3 or 1/10 DIN sensors are used in calibration and laboratory environments. Accuracy is typically expressed as ±(0.15 + 0.002·t)°C for Class A and ±(0.30 + 0.005·t)°C for Class B, where t is the temperature in °C. Standard RTDs reliably operate from –200 °C to +600 °C, though performance can degrade at the extreme ends of this range. The selection of RTD class depends on application requirements, balancing cost, precision, and environmental conditions.

Testing a Pt100 temperature sensor ensures accurate and reliable performance in industrial and laboratory applications. The most common method is to measure its resistance with a calibrated digital multimeter. At 0 °C, a Pt100 should read 100 Ω, with resistance increasing approximately 0.385 Ω per degree Celsius. By comparing measured resistance to standard Pt100 resistance tables, sensor accuracy can be verified. For higher precision, a temperature-controlled bath or dry block calibrator is used, allowing comparison against a traceable reference thermometer. It is also important to check for lead wire resistance, especially in 2-wire configurations, as this can introduce error. Regular testing and calibration in line with IEC 60751 standards help maintain measurement reliability and identify sensor drift or damage over time.