That is, the supply might be producing the correct voltage at its output terminals, but there will be a lower voltage at the input terminals of the load.
Very-high-impedance devices with ultralow leakage current require packages that do not allow stray current to flow, and may also have guard rings around input terminals.
Some laboratory quality ohmmeters, especially milliohmmeters, and even some of the better digital multimeters sense using four input terminals for this purpose, which may be used with special test leads.
In another form of receiving circuit the two input terminals are connected to a device designed to reverse polarity at predetermined intervals of time and charge a capacitor.