Which measuring system is classified as a resistance-temperature device (RTD)?

A resistance-temperature device (RTD) is specifically designed to measure temperature by correlating the resistance of the sensor with temperature changes. When the temperature of the RTD increases, its electrical resistance also increases in a predictable manner. This characteristic allows for accurate temperature measurement over a wide range.

Thermistors and RTDs both rely on changes in resistance with temperature, but thermistors typically have a non-linear response and are generally used for different temperature ranges compared to RTDs. While both thermistors and RTDs are used for temperature measurements, only RTDs have the specific properties that classify them as resistance-temperature devices.

On the other hand, thermocouples measure temperature through the voltage generated at the junction of two different metals, infrared thermometers measure temperature based on emitted infrared radiation, and optical pyrometers rely on the color of emitted light from heated objects without direct contact. These methods do not depend on a resistive element for their operation, which differentiates them from RTDs.