Resistors:
The unit of measurement for resistance is the Ohm. Of the three basic circuit components, resistors cause the
fewest measurement problems. This is true because it is practical to measure resistors by applying a dc signal or
relatively low ac frequencies. Resistors are usually measured at dc or low frequency ac where Ohm's Law gives
the true value under the assumption that loss factors are accounted for.
· Model
For low values of resistors (below 1kW) the choice usually becomes a low frequency measurement in a series
equivalent mode. Series because the reactive component most likely to be present in a low value resistor is series
inductance, which has no effect on the measurement of series R. For high values of resistors (greater than several
MW) the choice usually becomes a low frequency measurement in a parallel equivalent mode. Parallel because
the reactive component most likely to be present in a high value resistor is shunt capacitance, which has no effect
on the measurement of parallel R.