Metrication in the United States There are no U.S. customary units for electric current, potential difference, or charge since these concepts were developed after the international adoption of metric in science. The metric units ampere, volt, ohm and coulomb are the only units used. The SI term hertz has replaced the term "cycles per second" as a unit of frequency. Energy is often measured in watt hours, BTUs, therms or calories rather than the SI joule. Residential and commercial electrical energy use is metered and billed in kilowatt hours, kW·h, as in most metric countries. Force measurements regularly use the pound instead of the SI
Hartley (unit) digit, a ban corresponds to a decimal digit. A deciban is one tenth of a ban; the name is formed from "ban" by the SI prefix "deci-". One hartley corresponds to log(10) bit = ln(10) nat, or approximately 3.322 Sh, or 2.303 nat. A deciban is about 0.332 Sh. Though not an SI unit, the hartley is part of the International System of Quantities, defined by International Standard IEC 80000-13 of the International Electrotechnical Commission. It is named after Ralph Hartley. The term "hartley" is named after Ralph Hartley, who suggested in 1928 to measure information using a logarithmic base