Crossword Clue:

instrument for measuring speed of rotation

AnswerCrossword Clue
TACHSpeed measuring instrument (Abbr.)
PITOT... tube, for measuring air speed.
MFLOPSUnits for measuring computer system speed
RHEOMETERInstrument for measuring velocity of flow.
PALATOMETERInstrument for measuring movements of the velum.
AEROMETREInstrument for measuring density of air or gases: French spelling.