Which is the incorrect description about the measurement equipments used in inspection?
① The level has a built-in straight pipe that is containing an air bubble.
② The calipers is attached. with a vernier scale (vernier) obtained by dividing the (n-1)
scale of the main scale by n or n / 2.
③ Dial gauge has a built-in unit of rack and pinion.
④ Micrometer maintains constant measuring pressure by ratchet stop.