The Aberdeen chronograph was the first portable

gun chronograph A ballistic chronograph or gun chronograph is a measuring instrument used to measure the velocity of a projectile in flight, typically fired from a gun or other firearm. The instrument is often useful for tasks such as gauging the utility of a fi ...

, an instrument for measuring the

muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...

and striking power of a

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

fired by a

gun A gun is a device that Propulsion, propels a projectile using pressure or explosive force. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns or water cannon, cannons), or gas (e.g. light-gas gun). So ...

. It was invented in 1918 by

Alfred Lee Loomis Alfred Lee Loomis (November 4, 1887 – August 11, 1975) was an American attorney, investment banker, philanthropist, scientist, physicist, inventor of the LORAN Long Range Navigation System and a lifelong patron of scientific research. He esta ...

at the U.S. Army's

Aberdeen Proving Ground Aberdeen Proving Ground (APG) is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work at APG. There are 11 major commands among the tenant units, ...

. The method prevalent at the time was the Boulengé chronograph, which relied on the projectile passing through two wire screens. Breaking the first screen would release a rod held by

electromagnets An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a coil. A current through the wire creates a magnetic field which is concen ...

. While the rod was free-falling, breaking the second screen would activate a knife that marked the rod. Loomis' chronograph had a drum rotating at constant speed with a tape spooled inside. The projectile would pass through two screens, breaking the insulation between metal plates and creating a

short circuit A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...

. This created a spark that left two visible marks on the tape and measuring the distance between these marks would give the speed of the projectile. This method made it easier to measure the speed of larger shells and aircraft catapults. Loomis was issued a patent in 1921 for his chronograph.

References

{{reflist Ballistics American inventions