PT100 It is a commonly used temperature sensor; the “100” in its name indicates that its resistance is 100 ohms at 0°C. PT100 sensors are widely employed in applications requiring precise temperature measurement. As for the wiring configurations of PT100 sensors, these refer to how the sensor is connected. Common configurations include two‑wire, three‑wire, and four‑wire systems. The primary differences among these configurations lie in their measurement accuracy, signal transmission methods, and typical application scenarios.

1. Two-wire PT100

The two-wire PT100 is the simplest connection method, linking the PT100 sensor to the measurement circuit using only two wires. In a two-wire configuration, the resistance of the lead wires—which varies with ambient temperature and wire length—introduces measurement errors. Consequently, two-wire PT100 sensors are typically suited for applications where high measurement accuracy is not required, such as basic temperature monitoring and alarm systems.

The advantage of two-wire PT100 sensors lies in their simple structure and low cost, making them suitable for applications where cost is a key consideration. However, due to the measurement errors introduced by lead‑wire resistance, two‑wire PT100s offer relatively lower accuracy and cannot meet the requirements of high‑precision temperature measurements.

Two- and Three-Wire PT100

In a three-wire PT100 configuration, the sensor is connected to the measurement circuit via three wires: two carry the measurement signal, while the third serves as a common reference. By using three wires for signal transmission, this arrangement can partially compensate for errors caused by lead‑wire resistance, thereby enhancing measurement accuracy.

The measurement accuracy of a three‑wire PT100 is generally higher than that of a two‑wire PT100, making it suitable for applications with stringent accuracy requirements, such as industrial automation and laboratory testing. In addition, the three‑wire PT100 offers a degree of electromagnetic interference immunity, helping to mitigate the impact of external disturbances on measurement results.

However, the three-wire PT100 has a relatively complex structure and higher costs. Moreover, the requirement for three wires to connect it increases the complexity of installation and maintenance.

Three- and four-wire PT100

The four-wire PT100 uses four wires for connection: two carry the constant current source, while the other two transmit the measurement signal. In this configuration, because the constant current and the measurement signal are conveyed via separate pairs of leads, errors caused by lead resistance are completely eliminated, enabling highly accurate temperature measurements.

Four-wire PT100 sensors are typically employed in applications that demand exceptionally high measurement accuracy, such as precision temperature control and temperature calibration. Owing to their superior accuracy and strong immunity to electromagnetic interference, four-wire PT100s are widely used in fields including aerospace, semiconductor manufacturing, and precision instrumentation.

However, the four-wire PT100 has the most complex structure and the highest cost. Moreover, because it requires four wires for connection, installation and maintenance become correspondingly more complicated.

IV. Comparison of PT100 Sensors with Different Wiring Configurations

A comparison of two-wire, three-wire, and four-wire PT100 sensors—considering measurement accuracy, anti‑interference performance, cost, and application scenarios—reveals that each configuration has its own strengths and limitations. The two‑wire PT100 offers low cost but lower measurement accuracy; the three‑wire PT100 strikes a balance between the two‑wire and four‑wire types in terms of accuracy and noise immunity, making it suitable for applications with moderate precision requirements; meanwhile, the four‑wire PT100 delivers the highest measurement accuracy and the best anti‑interference performance, albeit at the highest cost.

In practical applications, the appropriate wiring configuration for a PT100 sensor should be selected based on specific requirements and operating conditions. For applications where measurement accuracy is not critical, a two‑wire PT100 may suffice; for general‑accuracy needs, a three‑wire PT100 is typically preferred; and for high‑precision temperature measurement and calibration, a four‑wire PT100 is the recommended choice.

In addition, when selecting PT100 sensor At the same time, it is also necessary to consider performance parameters such as its temperature range, response time, and stability to ensure that it meets the requirements of practical applications. Furthermore, when installing and using PT100 sensors, attention should be paid to proper wiring and calibration procedures to guarantee the accuracy and reliability of measurement results.