Common, passive, benchtop volt-ohm-milliammeters (multimeters) use a simple series
ohmmeter circuit, shown in simplest form in Figure 8.63, and have a nonlinear (hyperbolic)
scale on the D’Arsonval microammeter with zero ohms full-scale and infinite ohms at
zero deflection. A typical benchtop VOM series ohmmeter will have five RH ranges (RH is
the indicated RX at half-scale meter deflection), ranging typically from 12 Ω to 120 kΩ.
Inspection of the simple circuit shows that the DC meter current is given by
By Ohm’s law, the full-scale meter current is