manograph

Etymology
.

Noun

 * 1) An optical device for making pressure volume diagrams for high-speed engines, involving a light-tight box or camera having at one end a small convex mirror reflecting a beam of light onto the ground glass or photographic plate at the other end. The mirror is pivoted so that it can be moved so as to copy the motion of the engine piston on a smaller scale.

Translations

 * French: