Resistive temperature detectors (RTD) measure the change in the electrical
resistance of a wire-wound resistor with temperature, typically, a platinum
resistance element is used with a resistance of about 100 Ω. The resistance
change can be measured in a bridge circuit, but normally the resistor is driven
from a constant current source and the voltage developed across the resistor
measured. Care must be taken with these devices to ensure that the current
flowing through the devices is low to minimize the temperature changes occurring
due to the internal heating of the resistor.