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esr meter build

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by peter g, Aug 24, 2017.

  1. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I think, the way this meter works, that "(1000mfd on up)" is simply too large for the meter to read correctly.
    Did not read how this meter works. The one I have starts out with 1.0nF and 100uH and finds the resonance frequency. Then places the unknown cap across the 1.0nF reference cap and measures the frequency. Does math and displays the results.
    >I think C_unknown and C_ref need to be closer in value.
    >I think 100k ohms is not enough current for "(1000mfd on up)" to work right.
    >Yes I know this is how my meter measures C and not ESR.
    >Point is that my meter for measuring BIG capacitors does not work in this mode, at all. Different way.
    >Really big caps have problems that this meter can not deal with.
    upload_2017-8-31_6-58-58.png
     

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  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    • Informative Informative x 1
  3. dr pepper

    dr pepper Well-Known Member

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    Good points.
    If your building your own have a look at the superprobe project from mondo tech, I built one it measures caps by timing the charge period, it takes a while but it will measure 47,000 uF caps.
     
  4. dave

    Dave New Member

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  5. jjw

    jjw Member

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    This meter has a separate circuit and connector for electrolytic caps.
    It works by charging the cap through a resistor.
     
  6. peter g

    peter g Member

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    found this post from 2012:
    The negative value of ESR is some error, it hasn't been investigated fully yet, but there's been some talk on the topic, some time ago here on the forum, and someone has found that one of the Tantalum capacitors in the circuit affect this behaviour, more precisely the esr of that exact cap.
    Though if you zero the instrument, it should go to zero, and stay there at least till you switch it off and on again...
    So the negative value is because the esr of the measurement circuit of the instrument is drifting... and because, the reading is computed using a previously saved calibration value, this drifting can make the final measured value negative on the display...
    nd this post from 2012.
     
  7. peter g

    peter g Member

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    anyone have any comments on my last post?
     

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