What do you think of this Cap & ESR meter?

Discussion in 'The Projects Forum' started by timarlop, Nov 5, 2009.

  1. timarlop

    Thread Starter New Member

    Oct 27, 2009
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    0
    I'd like to do this Capacitance and ESR meter. It uses a 16x2 hd44780 compatible LCD, a PIC16F876A, a LM339 and a few transistors.

    The limitations:
    Capacitors smaller than about 10 microfarads cannot be measured for ESR. Capacitance down to 10 picofarads may be measured, however. Devices with appreciable leakage cannot be measured at all for capacitance.

    The bugs:
    The instrument hangs for a long time if a large capacitor is connected while it is measuring in the low capacitance range.

    What do you think of it? Any opinions welcome.
    Has anyone successfully built this meter?
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    A lot of typing to program the PIC, but looks good.


    ESR is really only relevant to electrolytics so perhaps the 10μ restriction is not too bad, although I would have preferred 1μ.

    Let us know how you get on if you build the project.

    PS Some great cartoons on other parts of that site. We could do with the AC / DC one here.
     
  3. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Looks like a fun project.

    If you're interested in estimating ESR, you can do it with a function generator and an AC voltmeter or scope (search the web, as there are a number of sites that explain how).

    I was able to get a B&K 886 LCR meter in trade for some consulting work a few years back (it was at a steep discount too, as I wouldn't pay that much money for an instrument I don't use every day). It replaced an old GR impedance bridge and I find it very handy and fast. I got it with the optional 4 wire probes, so it also measures milliohms well. Having used it for a while, I realize it can save a lot of time -- thus, if I was still a practicing scientist/engineer, I'd go ahead and spend the money for one, as it would be worth having in the lab in the long run.

    Edit: I forgot the reason I mentioned the B&K instrument: it measures ESR quite well.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    I use a "Blue ESR Meter" which works great for testing ESR in circuit, as well as battery health, such as AA alkaline and rechargeables. I found it's accuracy to be close to that of a Sencore analyzer with a 5 digit price tag, so for the price, I'm overjoyed. It comes in kit form with a pre-programmed uC.

    The device you are looking to build looks to have more features than the "Blue ESR meter", which only shows ESR in Ohms.

    ESR typically is only an issue when dealing with electrolytic capacitors over around 5uF. With smaller values, the Dissipation Factor is important, as well as other characteristics which would effect the Q of the cap, such as series and parallel inductance as well as resistance and leakage. Equipment to test those attributes tend to get expensive rather quick, due to the suggestion to test parameters at the frequency the capacitor or inductor will be used.
     
  5. alim

    Senior Member

    Dec 27, 2005
    113
    1
    I have an original Dick SMith ESR meter which is the fore runner to the BLUE ESR METER that you have. How do you use yours to measure battery health?
     
  6. nunoit@socal.rr.com

    New Member

    May 13, 2009
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    0
    can an esr meter be used to measure caps in circuit not just electrolitic
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    If you want an ESR meter, especially for testing caps in equipment repair, that is no good. Many of the caps that fail ESR are low values, 1uF, 2.2uF, 4.7uF etc. You really need a ESR meter that can test these.

    Altronics (australia) still sell the ESR meter kit, and it will do ESR testing in circuit and will do small electros. It's a good kit, I have a couple.
     
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