to tune the air-fuel ratio using a wideband oxygen sensor that is graphed along with the RPM. Integration of the dynamometer control system with automatic calibration tools for engine system calibration is often found in development test cell systems. In these systems, the dynamometer load and engine speed are varied to many engine operating points, while selected engine management parameters are varied and the results recorded automatically. Later analysis of this data may then be used to generate engine calibration data used by the engine management software. Because of frictional and mechanical losses in the various drivetrain components, the measured wheel brake horsepower is generally 15-20 percent less than the brake horsepower measured at the crankshaft or flywheel on an engine dynamometer. History The Graham-Desaguliers Dynamometer was invented by George Graham and mentioned in the writings of John Desagulier in 1719. Desaguliers modified the first dynamometers, and so the instrument became known as the Graham-Desaguliers dynamometer. The Regnier dynamometer was invented and made public in 1798 by Edmé Régnier, a French rifle maker and engineer. A patent was issued (dated June 1817) to Siebe and Marriot of Fleet Street, London for an improved weighing machine. Gaspard de Prony invented the de Prony brake in 1821. Macneill's road indicator was invented by John Macneill in the late 1820s, further developing Marriot's patented weighing machine. Froude Ltd, of Worcester, UK, manufactures engine and vehicle dynamometers. They credit William Froude with the invention of the hydraulic dynamometer in 1877, and say that the first commercial dynamometers were produced in 1881 by their predecessor company, Heenan & Froude. In 1928, the German company "Carl Schenck Eisengießerei & Waagenfabrik" built the first vehicle dynamometers for brake tests that have the basic design of modern vehicle test stands. The eddy current dynamometer was invented by Martin and Anthony Winther around 1931, but at that time, DC Motor/generator dynamometers had been in use for many years. A company founded by the Winthers brothers, Dynamatic Corporation, manufactured dynamometers in Kenosha, Wisconsin until 2002. Dynamatic was part of Eaton Corporation from 1946 to 1995. In 2002, Dyne Systems of Jackson, Wisconsin acquired the Dynamatic dynamometer product line. Starting in 1938, Heenan & Froude manufactured eddy current dynamometers for many years under license from Dynamatic and Eaton. See also Dynamometer car for railroad usage Engine test stand dynamometer for engines e.g., combustion engines Force gauge Fuel economy in automobiles Hand