Electronics

Sensors are specialized electronic devices that detect changes in quantities such as temperature, electrical power levels, chemical concentrations, physical position, fluid flow, or mechanical properties like velocity or acceleration. When a sensor responds to change, it usually requires a transducer to convert the quantity the sensor has measured into electrical signals that are translated into printouts, electronic readouts, recordings, or information that is returned to the device to control the change measured. Specialized resistors and capacitors are sometimes used as combined sensors and transducers. Variable resistors respond to mechanical motions by changing them to electrical signals. The thermistor varies its resistance with temperature; a thermocouple also measures temperature changes in the form of small voltages as temperatures are measured at two different junctions on the thermocouple. Usually, sensors produce weak electronic signals, and added circuits amplify these. But sensors can be operated from a distance and in conditions such as extreme heat or cold or contaminated environments where working conditions are unpleasant or hazardous to humans.