A kymograph (from Greek κῦμα, swell or wave + γραφή, writing; also called a kymographion) is an analog device that draws a graphical representation of spatial position over time.

[1][2] The kymograph was initially a mechanical and hydraulic device, invented by German physiologist Carl Ludwig in the 1840s, and found its first use as a means to monitor blood pressure.

The blood pressure was conveyed by hydraulics and levers to move a stylus that scratched a white trace into soot-covered paper on the revolving drum.

Throughout the nineteenth and twentieth centuries, researchers and technicians devised many improvements to the device, plus numerous new sensory components to measure a wide range of physiological phenomena such as breathing, muscle movement, and speech.

[3] Kymographs were also used outside medical science to measure atmospheric pressure, tuning fork vibrations, the functioning of steam engines, animal habits, and the movement of molecules in cells.