Ammeter metering energy (the charge needs to be multiplied by the voltage to give energy) or for estimating the charge of a battery or capacitor. A picoammeter, or pico ammeter, measures very low electric current, usually from the picoampere range at the lower end to the milliampere range at the upper end. Picoammeters are used for sensitive measurements where the current being measured is below the theoretical limits of sensitivity of other devices, such as Multimeters. Most picoammeters use a "virtual short" technique and have several different measurement ranges that must be switched between to cover multiple decades of measurement. Other
William Edward Ayrton electrical engineering, or of applied physics, at the Central Technical College, South Kensington. He published, both alone and jointly with others, a large number of papers on physical, and in particular electrical, subjects, and his name was especially associated, together with that of Professor John Perry, with the invention of a long series of electrical measuring instruments, including the spiral-spring ammeter, and the wattmeter. They also worked on railway electrification, produced a dynamometer and the first electric tricycle. Ayrton is also known for his work on the electric searchlight. Ayrton died in London in 1908 and is buried in Brompton