electric eye vs sensing element

electric eye and sensing element both are nouns.

Word	Noun	Adjective	Verb	Adverb
electric eye	Yes	No	No	No
sensing element	Yes	No	No	No

As nouns, sensing element is a hypernym of electric eye; that is, sensing element is a word with a broader meaning than electric eye:

electric eye: a transducer used to detect and measure light and other radiations
sensing element: 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

Other hypernyms of electric eye include detector, sensor, transducer.

electric eye (noun)	sensing element (noun)
a transducer used to detect and measure light and other radiations	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