A resistance temperature detector (RTD) is a type of temperature sensor that measures temperature by sensing the change in resistance on the surface. These RTD sensors are small, have quick response times, and offer high-temperature sensitivity. Owing to their immense popularity, several different types of RTDs are used in multiple industries for various purposes. The common types are 1,000 ohms and 100 ohms, which are integrated into temperature probes, bolt-on sensors, and surface-mount sensors. Among all types of RTDs, the surface-mount RTD are quite popular in the industry due to their easy installation and superior protection. This post provides an overview of surface-mount RTD sensors and their configuration capabilities and applications.

Surface-mount RTDs are platinum thin-film temperature sensors. These thin-film RTDs are often manufactured through thin platinum layer deposition on resistive material surfaces. An electric circuit pattern is etched on a platinum or brass surface to measure resistive changes. The surface-mount RTDs are often manufactured in compliance with the European DIN/IEC 60751 standard. Depending on their application, the materials used vary. For example, surface-mount RTDs can be in Kapton® or silicone. Also, as they are created on resistive metal surfaces, they have adhesives on one side. A pressure-sensitive adhesive (PSA) is applied to the back of the heater for ease of application. Further, surface-mount sensors have several wire configurations, lead elements, and termination types.

Similar to general RTD configurations, surface-mount RTDs have different lead configuration types:

Two-Wire Configuration: This is the simplest configuration of surface-mount RTDs. In this type, a single wire connects to two ends of the RTD in series with the resistive surface.

Three-Wire Configuration: The three-wire surface-mount RTD configuration is the most preferred in industrial applications. In this type, two wires are connected to two different ends of the sensing material, creating a bridge, which makes resistive difference calculation precise. For process temperature monitoring, this type of configuration is used.

Four-Wire Configuration: This is the most complex surface RTD configuration. In this type, the surface sensing material is integrated with four leads, an external power source, and three resistors. This type works on zero temperature resistance. Therefore, it is most sensitive to resistive temperature change.

The following are the common applications of surface-mount RTDs: