Sensor Definition A sensor is a device that converts a physical or chemical quantity into an easy-to-use electrical signal. The International Electrotechnical Committee (IEC) is defined as: "A sensor is an antecedent component of a measurement system that converts an input variable into a measurable signal." According to Gopel et al., "A sensor is a sensor that includes a carrier and a circuit connection," while a "sensor system is a system that combines the power of some sort of information processing (analog or digital)." The sensor is an integral part of the sensing system and is the first pass through which the measured signal is input.
Sensors convert some form of energy into another form of energy. There are two types: active and passive. Active sensors can transform one form of energy directly into another without the need for an external source of energy or stimulus.