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Which Frequency setting to read capacity on an Extech 380193?

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  • Which Frequency setting to read capacity on an Extech 380193?

    Hi, I'm using an Extech 380193 but I wasn't really taking capacity readings in the past. I started to make notes in 1 KHz mode since that is where I also take Q readings. Not sure if 1 Khz is the right or better say the most common setting rather than the 120 Hz setting. With having numbers in mind that more conveniently compare to other winders' notes I wonder which frequency setting is the most commonly used setting to read capacity of a pickup coil? 1 Khz or 120Hz?
    Thanks in advance

  • #2
    Because of the interaction between inductance and capacitance, LCR meters don't give reasonable readings of PU (distributed) capacitance at 120Hz and 1kHz.
    There are other threads on the MEF, where C-measurements are discussed in more detail. Search for PU capacitance or distributed capacitance.
    The standard method is measuring the frequency response of the PU impedance and calculating the capacitance from the resonance peak frequency.

    PU capacitance is typically much smaller than the cable capacitance, which acts in parallel, and thus variations have hardly any influence on the PU sound - the influence of cable capacitance/length is always much stronger. The variation in PU capacitances is rarely more than 100pF, which has the same sound effect as a change of cable length by 1m.
    Last edited by Helmholtz; 11-14-2018, 01:11 PM.
    - Own Opinions Only -

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    • #3
      Will look it up and read. Thank you.

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      • #4
        The LCR meter has to be able to test above 100kHz (and set to "PAR" more) to get a reasonable capacitance reading. The DE-5000 can do it, I'd recommend it over an Extech, both because it's cheaper and because it does more. Unfortunately it was discovered that secondary resonances can and do occur in a pickup coil (most likely due to non-uniformity in how how the coil wire is laid), and if one of those higher resonances is near that the 100kHz test frequency, you will get a bad reading. You can check for the C value since it's convenient to do so, but can't necessarily count on it always being accurate.

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        • #5
          Thanks for the interesting information. I will probably not gonna fuzz around w. capacity within the next future. Will stick on the parameters that I used to work with and then in the end there's also ears Thanks again

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          • #6
            The standard frequency for audio measurements is 1 KHz, basically set in the days when audio meant telephone.

            Measurement at 10 KHz and 100 KHz are not reliable ways to measure coil self-capacitance.

            For reliable measurements of self capacitance, use Terman's method. There was a big debate about this. See:

            https://music-electronics-forum.com/...ad.php?t=36537

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