Insulation resistance measurements

I am not saying anything new when I say that d-c electrical conductance or conductivity (reciprocal resistance or resistivity) of electrical insulating materials is not generally a property of major concern to the user of these materials. In fact, the conductance of an insulating unit is usually several orders of magnitude smaller than is required for efficient use. Only in those cases where extremely small currents are involved do the actual values of the conductances become important as such. The author discusses ASTM D 257 conductance measurement techniques.