sensors

A sensor is a type of transducer which uses one type of energy, a signal of some sort, and converts it into a reading for the purpose of information transfer. A mercury thermometer is an example of a sensor that converts the expansion and contraction of a volume of mercury in response to change in temperature (the signal), to a reading on a calibrated glass tube giving information about ambient temperature. Other sensors, such as a thermocouple, produce an output voltage or other electrical output which may be attached to a meter for reading a change or interpreted by another device (such as a computer). For accuracy in the application a calibration of the sensor and its output information is necessary.

Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include automobiles, machines, aerospace, medicine, industry, and robotics.

A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. For instance, if the mercury in a thermometer moves 1cm when the temperature changes by 1°, the sensitivity is 1cm/1°. Sensors that measure very small changes must have very high sensitivities.