LCR Meter vs Impedance Analyzer

August 11, 2017 by Tim Ashworth

We are often asked about the difference between LCR meters and impedance analyzers, especially given that the MFIA Impedance Analyzer combines the functionalities of both instruments.

LCR meters and impedance analyzers are fundamentally similar, in that they both measure impedance parameters such as capacitance, inductance and resistance.They achieve this by measuring the phase-sensitive voltage-to-current ratio. This ratio gives the fundamental impedance values such as absolute impedance and phase, along with the real and imaginary parts of impedance.

From these fundamental values, impedance parameters can be derived by applying a user-defined equivalent circuit model. These parameters include capacitance, inductance and resistance (hence the name LCR meter). In addition, further parameters including Q-factor, dissipation and conductance can also be derived.

An impedance analyzer includes this functionality but also offers the capability to sweep the frequency and graphically display the acquired impedance parameters. This is different from LCR meters, which acquire data at a fixed frequency. That said, some LCR meters may perform measurements at many different fixed frequencies, so that impedance parameters can be interpolated from the data in an additional step.

Figure 1: LabOne screenshot showing the Numeric tab of the MFIA. The device under test is a 10 mH SMD. The test signal is 0.5 V and the test frequency is 100 kHz.

To access the LCR meter functionality of the MFIA, select the Numeric tab as shown in Figure 1. Here it’s possible to view the fixed measurement frequency and acquired impedance parameters. The Numeric tab can be freely configured to show the parameters relevant to your experiment, and any fixed frequency can be selected between 1 mHz and 5 MHz. With the MF-MD upgrade option you can even measure simultaneously at two different frequencies.

The values displayed in the Numeric tab can also be plotted in the time domain using the Plotter tool as shown in Figure 2. The Plotter displays multiple parameters as a function of time, and allows you to export the display in vector graphics or the data in csv format for further analysis.

Figure 2: LabOne screenshot showing the Plotter tab. It displays the selected impedance parameters as a function of time, in this case, abs(Z), phase and inductance. The horizontal scale is time (in seconds) passed after starting the measurement.

To use the MFIA as an impedance analyzer, open the Sweeper tab as shown in Figure 3. The Sweeper allows you to sweep the measurement frequency (as well as other parameters such as the offset bias) and acquire impedance parameters as a function of frequency. The auto-range function of the Sweeper ensures that you can sweep continuously from 1 mHz to 5 MHz and all the range changes are handled automatically.

The MFIA is both a precision LCR meter and an impedance analyzer, and you can seamlessly switch between these capabilities. Furthermore, you can take advantage of both functionalities simultaneously on the MFIA thanks to the powerful LabOne software, which allows multiple tabs to operate at the same time. This means you don't have to choose between an LCR meter and an impedance analyzer - you can now have both in one instrument.