speedometer vs velocimeter

speedometer

noun
  • Such a device incorporating an odometer. 

  • An instrument located within the dashboard of a vehicle that measures and indicates the current speed of the vehicle. 

velocimeter

noun
  • A device used to measure the velocity of something, such as an object or a wave 

How often have the words speedometer and velocimeter occurred in a corpus of books? (source: Google Ngram Viewer )