Specifications

Most of the modern impedance measuring instruments basically measure vector impedance (R + jX)
or vector admittance (G + jB) and convert them, by computation, into various parameters, Cs, Cp,
Ls, Lp, D, Q, |Z|, |Y|, q, etc. Since measurement range and accuracy are specified for the impedance
and admittance, both the range and accuracy for the capacitance and inductance vary depending on
frequency. The reactance chart is also useful when estimating measurement accuracy for capaci-
tance and inductance at your desired frequencies. You can plot the nominal value of a DUT on the
chart and find the measurement accuracy denoted for the zone where the DUT value is enclosed.
Figure 1-21 shows an example of measurement accuracy given in the form of a reactance chart.
The intersection of arrows in the chart indicates that the inductance accuracy for 1 µH at 1 MHz is
±0.3 percent. D accuracy comes to ±0.003 (= 0.3/100.) Since the reactance is 6.28 Ω, Rs accuracy is
calculated as ±(6.28 x 0.003) = ±0.019 Ω. Note that a strict accuracy specification applied to various
measurement conditions is given by the accuracy equation.
Figure 1-21. Example of measurement accuracy indicated on a reactance chart
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