Class of accuracy in electrical measurements in series with the load, so the same current flows through the load and the ammeter. The voltmeter is used in parallel with the load, so the voltage between the two terminals of the load is equal to the voltage between the two terminals of the voltmeter. Ideally the measuring device should not affect the circuit parameters i.e., the internal impedance of the ammeter should be zero (no voltage drop over the ammeter) and the internal impedance of the voltmeter should be infinite (no current through the voltmeter). However, in actual case, ammeters have a low but non zero impedance
Manganin Manganin Manganin is a trademarked name for an alloy of typically 84% copper, 12% manganese, and 4% nickel. It was first developed by Edward Weston in 1892, improving upon his Constantan (1887). Manganin foil and wire is used in the manufacture of resistors, particularly ammeter shunts, because of its virtually zero temperature coefficient of resistance value and long term stability. Several Manganin resistors served as the legal standard for the ohm in the United States from 1901 to 1990. Manganin wire is also used as an electrical conductor in cryogenic systems, minimizing heat transfer between points which need electrical connections.