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esr meter build

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

  1. peter g

    peter g Member

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  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    How do you know this?
     
  3. peter g

    peter g Member

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    that's what I've read.
     
  4. dave

    Dave New Member

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  5. peter g

    peter g Member

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    I mean I've tested it on electrolytic caps and it shows a neg value.
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Then there is a fault in the software.
     
  7. peter g

    peter g Member

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    hi nigel, there are several versions of the software. the reason I picked this one is that it shows three parameters of c.u.t. this is a fairly old project, I would think the designer would have corrected any bugs.
     
  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    If it's displaying negative values, then there's certainly got to be a software problem - as it shouldn't be able to do that - who would write a program with the capability of displaying negative values for something which can only ever be positive?.
     
  9. peter g

    peter g Member

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    so, you don't think its a circuit problem?
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It could well be, BUT if it has the capability of displaying a negative number then there's an obvious software problem as well.
     
  11. Pommie

    Pommie Well-Known Member Most Helpful Member

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    It's probably using itoa(int to asc) function which will display negative numbers. This suggests that it is measuring resistance higher than 32767 which would be a circuit problem.

    Mike.
     
  12. peter g

    peter g Member

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    hi nigel, I programmed the chip with another hex code for this meter. the same neg esr condition exists?
     
  13. peter g

    peter g Member

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    hi pommie, could you point me where I might look for the circuit problem?
     
  14. peter g

    peter g Member

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    I built three of these meters and they all have the same problem with neg esr readings. the rest of the meter works!
     
  15. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    or higher than 127 if 8 bit number.
    How about taking a really good 10uF cap or 1uF that we know has low ESR, (non electrolytic) and make certain it works right.
    Then solder a 1 ohm resistor in series. (0.1 ohm, or 10 ohm something small) It should read 1 ohm more.
    Then increase the resistance a little at a time. I could be that at some value the number flips negative. (What Pommie said)

    Can you imagine that anyone could get mixed up about signed/un-signed numbers. LOL
     
  16. peter g

    peter g Member

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    hi ron, o.k. I will do that and post back. btw, in case you haven't guessed my electronic knowledge is limited to fixing TV's.
     
  17. peter g

    peter g Member

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    o.k I got up to 65 ohms display did not turn negative. at 66 ohms the meter stopped reading esr, just a question mark.on a different tack it seems that the esr value to be correct depends a lot on what the Vesr voltage is. when its hi(180 millivolts or more it works)?
     
  18. peter g

    peter g Member

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    it also is more prone to go negative on hi value caps(over 1000ufd).
     
  19. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Those really big caps have a leak problem. Some meters can not read capacitance with more than 1mA of leakage. Just a thought.
     
  20. peter g

    peter g Member

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    this meter has the ability to read leakage(tan delta?)
     
  21. Pommie

    Pommie Well-Known Member Most Helpful Member

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    The meter reads in mΩ and therefor above 32Ω will display as negative. Int to Asc on microcontrollers takes a 16 bit number so it should be above 32767 that is negative.

    Mike.
     

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