I am not sure, but going from memory, this may be a Siemens scale. This
has to do with very high impedance readings.

The Siemens scale is based on conductivity, derived from inverse
resistance. This would then would be nS = nano-Siemens, and mS would be
milli-Siemens.

This link is about a dedicated Siemens meter, just to give an
explanation of what the Siemens scale is about.
http://www.trifield.com/HighResistance.htm

The Siemens scale is used for testing insulation factors, and very high
resistance values. There is also an instrument called a megger that is
used for testing very high resistances of materials, and especialy the
break down resistance of insulator materials. There are meggers that
also use very high voltages for the testing, in order to determine the
if the insulation material will easily break down and start to condcut
under use with voltage applied.

Jerry Greenberg
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