deciampere
An SI unit of electrical current equal to 10⁻¹ amperes. Symbol: dA
deciampere: one-tenth of an ampere, rarely used
A deciampere is a unit of electrical current equal to 0.1 amperes, derived from the SI prefix deci- and the ampere base unit. It measures the flow of electric charge at a scale that falls between the milliampere (mA) and the ampere (A). In practical terms, 1 deciampere equals 100 milliamperes, a relationship that explains why this unit sees almost no use in industrial or laboratory work.
The deciampere exists formally within the SI system but occupies an awkward middle ground. Most measurements in electronics and electrical testing use either milliamperes for precise control circuits and sensor signals, or amperes for power distribution and motor ratings. A current of 0.1 A is neither small enough to require the precision of a decimal prefix nor large enough to warrant stepping up to higher units. Engineers and technicians simply say "100 milliamps" rather than "1 deciampere" because the former term is clearer and more commonly referenced in equipment specifications.
Where the deciampere fails in practice
Equipment design and documentation almost never specify current in deciamperes. Industrial power supplies, control relays, and safety circuits reference current in milliamperes or amperes. Meters and multimeters display current in mA or A; no standard instrument has a deciampere scale or mode. Test procedures, circuit diagrams, and technical standards across metallurgy, chemical processing, and manufacturing deliberately avoid this unit, making it a theoretical construct rather than a working tool.
The deciampere exists in SI conversion tables and standards documents because SI permits any combination of base units and metric prefixes. However, metrologists and standards bodies recognize that not every permitted unit serves practical needs. When current measurement is required in industrial metrology, the relevant standards specify results in amperes or milliamperes depending on the magnitude, bypassing the deciampere entirely. It remains a footnote in SI documentation rather than a working term in the electrical trades.