tach vs tachograph

tach and tachograph both are nouns.

Word	Noun	Adjective	Verb	Adverb
tach	Yes	No	No	No
tachograph	Yes	No	No	No

As nouns, tachograph is a hyponym of tach; that is, tachograph is a word with a more specific, narrower meaning than tach:

tach: measuring instrument for indicating speed of rotation
tachograph: a tachometer that produces a graphical record of its readings; used to record the speed and duration of trips in a motor vehicle

tach (noun)	tachograph (noun)
measuring instrument for indicating speed of rotation	a tachometer that produces a graphical record of its readings; used to record the speed and duration of trips in a motor vehicle