The impedance of real-world passive components depends on frequency, signal level and DC bias. This has to be taken into account during circuit design. The R&S®LCX LCR meter is ideal for measuring these dependencies. The R&S®LCX sweep tool is an application program for conveniently performing such sweeps and displaying the results on charts.
The impedance of real-world passive components like resistors, capacitors and inductors always deviates from the ideal value depending on the technology and dimensions of the component. Parasitic elements, like inductance and resistance of leads as well as capacitance between windings of a coil, have a major impact on the properties of the component. The impedance of parasitic elements largely depends on the frequency. This has to be considered in designing electronic circuits.
Equivalent circuits of passive components
To some extent, the properties of passive components depend on the amplitude of the applied AC current or voltage signal and on a superimposed DC bias. Two examples are discussed in the next paragraphs.
Coil dependency
The core material used in inductors and transformers always exhibits nonlinear behavior. In small magnetic fields, coercivity causes hysteresis losses. In strong magnetic fields, the magnetic flux approaches saturation. The loss in the inductor increases with increasing signal amplitude and with increasing superimposed DC current.
Capacitance dependency
In ceramic capacitors, the dielectric constant of dielectric material with high permittivity can vary significantly with the applied field strength. As a consequence, the capacitance of capacitors made from such materials will change with an applied DC bias voltage.
The R&S®LCX LCR meters precisely measure the complex impedance of passive components in the frequency range from 4 Hz to 300 kHz or to a maximum of 10 MHz, respectively. The dynamic impedance measurement function of the R&S®LCX-K106 advanced analysis functions option executes the measurements with swept test signal frequency, level or bias. It also collects the results in a log file. The built-in ChartView gives a quick qualitative overview that shows the dependency of the measurement results on the swept parameter.
A wealth of configuration and visualization possibilities is added with the free-of-charge R&S®LCX sweep tool, available on the Rohde&Schwarz website. The application program remote-controls the R&S®LCX with a sweep of frequency, test signal level or DC bias. Complex impedance and admittance as well as inductance, capacitance, quality and loss factor, resistance and reactance are plotted in diagrams versus the swept parameter. In addition, impedance and admittance are plotted on the complex plane in Nyquist diagrams.
The R&S®LCX LCR meters are the ideal solution to precisely measure complex impedance, resistance, inductance and capacitance of passive components as well as their dependence on frequency, signal level and DC bias. The R&S®LCX sweep tool (application note 1GP132) adds extra value with comfortable automation and charting possibilities. For advanced applications, the Zurich Instruments MFIA impedance analyzer is a perfect complement to the R&S®LCX LCR meters
Admittance, capacitance and loss factor of an electrolytic capacitor versus frequency
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