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FNIRSI LC1020E Auto-Magic Responsiveness

scottiebabe

To test the responsiveness of my new LCR meter, I soldered a 10 nF capacitor in parallel with a 50 kOhm potentiometer (configured as a rheostat) and twiddled the potentiometer shaft.

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I used the 4-wire kelvin clips (which work great btw) and configured the meter to auto-identify and auto-range with a test frequency of 1 kHz.

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Here is a video of display updating

The measurement update rate and identification time is more than fast enough for my needs. Once the meter settles on a range and component type, it reverts to a slow update speed (presumably it is average a few readings together too, but I don’t know).

I don’t understand how the “auto” series vs parallel readout works, there is no noticeable annunciation indicating which calculation it is using. So, I would recommend manually choosing a topology yourself, in the video I had the meter in “series” mode.

The capacitance changing with resistance is the correct result for the series readout mode in the video. The two circuits below are equivalent at 1kHz

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This is significantly faster than most equivalently priced DMMs auto ranging performance on DC volts or resistance. It is also what I would expect of a product in 2025 having a 32-bit MCU with floating point hardware running at tens of megahertz.

It is unfortunate the measurement performance at 100 kHz is so lousy, otherwise it would be easy to recommend the meter for the price.

  • s a basic sanity test, I measured a few resistors and capacitors independently and as a series combination. This isn’t a metrology grade validation test, but it is reasonably fair, as I am letting the meter measure the components independently itself and considering the measurement as “truth”. I choose a few RC combinations randomly off the top of my head.

    image

    In a perfect world, with a perfect meter, the sum of the independent measurements should match the measurement of the series circuit; as impedances are additive in series.

    The first combination I choose was a 10 nF capacitor and a 1.6 kOhm resistor. I then recorded the resistance and reactance displayed on screen

    R = [(1.6373e3 - 0.16j) (1.6362e3 -3.3j) (1.6342e3 -32.4j) (1.3923e3 -579.1j)];
C = [(18.15e3-163.6e3j) (17.331-16.325e3j) (7.8325-1.6458e3j) (10.248-159.95j)];
RC =[(1.9220e3-163.2e3j) (1.6739e3-16.358e3j) (1.6122e3-1.6816e3j) (1.4640e3-396.72j)];

    The resistor measured as approximately 1.6k Ohms with a small amount of reactance (which is largely the error of the meter). The capacitor measured as expected as a function of frequency. The 100 kHz measurements are way off.

    A summary of the amplitude and phase errors of the measured and expected values is shown below:

    *** DUT = 10 nF + 1.6 kOhms ***
ftest = 100 Hz, 1 kHz, 10 kHz, 100 kHz
Amplitude Error (A_e): -0.96 %, +0.19 %, -0.78 %, -4.32 %
Phase Error (Theta_e): -6.22 °, +0.06 °, -0.58 °, +12.62 ° 


*** DUT = 820 nF + 50 Ohms ***
ftest = 100 Hz, 1 kHz, 10 kHz, 100 kHz
Amplitude Error (A_e): -0.01 %, -0.13 %, -0.76 %, -0.95 %
Phase Error (Theta_e): +0.00 °, -0.18 °, -0.31 °, +0.38 ° 


*** DUT = 470 uF + 10 Ohms ***
ftest = 100 Hz, 1 kHz, 10 kHz, 100 kHz
Amplitude Error (A_e): +0.01 %, -0.04 %, -0.06 %, +0.24 % 
Phase Error (Theta_e): -0.08 °, -0.01 °, +0.37 °, -5.41 °
  • in reply to scottiebabe

    Is there a particular 100 kHz measurement that I can replicate on my meter? To see if it has the same issues?

  • in reply to Jan Cumps

    Yes, you can try measuring any carbon film resistor from 100 ohms and up, they don't have significant series inductance. You should measure the same resistance and negligible reactance across all frequencies.

    For example the meter measures a 1 MOhm resistor as almost 5 MOhms at 100 kHz, that is totally wrong.

    image

    behavior of the unit is similar for other resistors too at 100 kHz,

    image

    If you can try measuring a few resistors above 100 ohms across frequencies it would be an excellent reference point.