For centuries people were only able to grasp temperatures subjectively as cold or hot. The invention of the first objective temperature measuring device based on the expansion of air goes back to Galileo Galilei approx. in 1592.
Today, temperature measurement technique disposes of a great number of highly specialized sensors and methods that allow to determine exactly and reproduce the thermodynamic state of the matter and thus, its temperature almost between 0°K and, for example, the temperature of the sun.
Electric thermometers turn the physical value of temperature into a dependent signal. They are self-contained constructive components that deliver an output signal for further treatment. Dependent on the sensor principle, in most cases an auxiliary energy source is necessary.
An important advantage results out of the good transferability of those electric symbols over far distances. The transducer and indicator of temperature can be situated far away from each other. The measuring signals can be integrated and treated with small effort into control respectively process guiding systems.