RTD stands for Resistance Temperature Detector, which refers to a type of temperature sensor. As the name suggests, it uses changes in resistance to detect temperature, but that in itself might not tell you how an RTD works.

When the temperature increases, the RTD’s resistance increases, and vice versa. The control system or transmitter constantly sends a current through the RTD sensor. When the temperature changes, the resistance on the current can increase or decrease.  Here, the RTD detects this shift and thereby reports it.

Vendors build RTD sensors out of a variety of materials. Platinum, copper, and nickel show up the most often, with platinum as the fan favourite because it offers the best stability in a wide range of temps.

Also, we can choose RTDs with two, three, or four wires, but what does that mean? These wires create the compensation you need for the cable. Of course, the two-wire option doesn’t, so we should choose it when you need only an approximate value. The three-wire option is most common in many applications.

Many factors influence the properties of an RTD sensor. Various materials, such as platinum, copper, or nickel, can affect the range and linearity. Element types can have effects too, like thin-film elements or wire-wound elements. We can also have sensors with two, three, or four wires. The most common version is three, but each option has its pros and cons.

If you need help choosing the right temperature sensor for your application, take a look at our new temperature measurement smart assistant.