Interferometer and Dynamometer

noun

• Any measuring instrument that uses interference patterns to make accurate measurements of waves. .

(n.) An instrument for measuring small movements, distances or displacements by means of the interference of two beams of light; -- called also refractometer.

noun

• Measuring instrument designed to measure power.
  • synonyms: ergometer

(n.) An apparatus for measuring force or power; especially, muscular effort of men or animals or the power developed by a motor or that required to operate machinery.