detector

n. person or thing that detects; sensor

A sensor is a type of transducer. Direct-indicating sensors, for example, a mercury thermometer, are human-readable. Other sensors, such as a thermocouple, only produce an output voltage or other electrical output which must be interpreted by another device (such as a computer). Most sensors are electrical or electronic, although other types exist.
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Detector /de·tec·tor/ an instrument or apparatus for revealing the presence of something. lie detector polygraph. [more]Detector - Community and Resources

Noun
1. any device that receives a signal or stimulus (as heat or pressure or light or motion etc.) and responds to it in a distinctive manner
(synonym) sensor, sensing element
(hypernym) device
(hyponym) metal detector
(derivation) detect, observe, find, discover, notice
2. rectifier that extracts modulation from a radio carrier wave
(synonym) demodulator
(hypernym) rectifier
(part-holonym) radio receiver, receiving set, radio set, radio, tuner, wireless
3. electronic equipment that detects the presence of radio signals or radioactivity
(hypernym) electronic equipment
(hyponym) crystal detector
(part-holonym) radio receiver, receiving set, radio set, radio, tuner, wireless
(derivation) detect, observe, find, discover, notice

n. detector, sensor