A sensor is a device that can read and measure input, such as heat, motion, pressure and moisture, from its physical environment and output the results as readable data. Transducers, such as antennas, stereo speakers and thermostats, convert one kind of energy to another. Some devices have both sensors and transducers.
Electronic sensors measure physical phenomena and convert their measurements into electronic signals. Sensors respond to stimuli by changing electric resistance, changing current flow or changing voltage output. Sensors are either analog – yielding measurements that vary across the sensor’s input range – or digital – having only two states, on or off, like a light switch. Analog and digital sensor technology can be combined to produce digital readouts from analog data.
Although transducers and sensors often work in combination, any device that converts energy is a transducer. Like sensors, transducers are common measuring instruments and are used to convert signal from one form of energy to another. For example, a transducer designed to measure pressure read the mechanical data then convert it to electronic signal for display on a readout. Dynamic stereo speakers, or electroacoustic transducers, convert electronic audio signal into sound. Types of transducers include electrical, mechanical, electromagnetic, light, chemical acoustic and thermal.