vernier caliper vs vernier micrometer

vernier caliper and vernier micrometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
vernier caliper	Yes	No	No	No
vernier micrometer	Yes	No	No	No

As nouns, vernier caliper and vernier micrometer are synonyms defined as:

vernier caliper and vernier micrometer: a caliper with a vernier scale for very fine measurements

vernier caliper (noun)	vernier micrometer (noun)
a caliper with a vernier scale for very fine measurements	a caliper with a vernier scale for very fine measurements