The very high internal resistance of digital multimeters, in
their voltage-measuring ranges, can be used to measure extremely
low currents (even though the DMM may not offer a low current range
explicitly). Suppose, for example, you want to measure the small
current that flows through a 1000 M ohm "leakage" resistance (that
term is used to describe a small current that ideally should be
absent entirely, for example through the insulation of an
underground cable). You have available a standard...