Decisiemens

Decisiemens (symbol dS) is the derived SI unit of electrical conductance, the reciprocal of resistance. Conductance G is defined as G = 1/R, so the decisiemens represents one tenth of a siemens: 1 dS = 0.1 S. Consequently, 1 S = 10 dS. In terms of other submultiples, 1 S equals 1000 mS, so 1 dS equals 100 mS.

The decisiemens is rarely used in modern instrumentation; conductance is more commonly expressed in siemens (S), millisiemens (mS), or microsiemens (µS). Because 1 dS = 0.1 S, it can appear in contexts where values are specified in tenths of a siemens. A practical example is a resistor of 10 ohms, which has a conductance of 0.1 siemens, i.e., 1 decisiemens.

History and usage notes: The term mirrors the SI framework of prefixes, with deci- meaning a factor of 0.1. The unit name aligns with the older “siemens” for conductance. In most contemporary texts, however, decisiemens are not common, and measurements are reported in siemens, millisiemens, or microsiemens. The decisiemens remains a valid but uncommon unit for expressing conductance in tenths of a siemens.