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finding capacitor polarity — Parallax Forums

finding capacitor polarity

agimuhingagimuhing Posts: 39
edited 2011-08-11 15:56 in General Discussion
I got this capacitor from a grab bag

P8110002.JPG

P8110004.JPG

P8110001.JPG
<- the pin on the left has a polarity marking
P8110003.JPG


appears to be electrolytic because there is a can inside the casing
also has a black polarity marking above one of the pins

But is the marked pin positive or negative?

the cap also appears to be surface mount, but I've never seen a package like this before
What device might this be found in?
P8110002.JPG
349 x 335 - 30K
P8110004.JPG
861 x 1108 - 136K
P8110001.JPG
402 x 508 - 41K
P8110003.JPG
395 x 543 - 41K

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-08-11 08:41
    But is the marked pin positive or negative?

    Ummm... Yes! :zombie:

    Some electrolytics noted Pos and others noted Neg.
    I don't think I've ever seen a tantalum marked other than Pos.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-11 09:57
    Are you sure it's a cap? Aside from the markings, it looks more like a crystal.

    -Phil
  • agimuhingagimuhing Posts: 39
    edited 2011-08-11 13:41
    I hooked it up to a multimeter measuring resistance, and the capacitor/crystal/mystery component's resistance slowly increased to infinity. I don't think crystals do that.

    Also, the increase to infinity was faster when the cap was hooked up to the multimeter in a certain direction.
  • ercoerco Posts: 20,259
    edited 2011-08-11 13:45
    Flux capacitor? :)

    It does sound like an electrolytic from your multimeter test. Dunno how to tell polarity. Make sure it was fully discharged for your multimeter timimg tests.
  • agimuhingagimuhing Posts: 39
    edited 2011-08-11 14:06
    I know that capacitors have leakage. Electro caps have more leakage when installed backward. My dad said that he was able to tell the polarity of a cap by hooking it up to an analog multimeter and measuring its resistance. The problem is my multimeter is digital and doesn't do that very well
  • ercoerco Posts: 20,259
    edited 2011-08-11 14:15
    http://www.physicsforums.com/showthread.php?t=99017

    reply #2 agrees with agimuhing. multimeter infinite resistance connection shows correct polarity, wrong polarity shows leakage (finite high resistance)
  • agimuhingagimuhing Posts: 39
    edited 2011-08-11 14:28
    my multimeter shows infinite resistance both ways the capacitor is connected.
    time to find an amp unless someone else has a solution
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2011-08-11 15:09
    I know this sounds bad but blow one up !

    it it go BOOOM then its the wrong way .........

    Peter
  • ercoerco Posts: 20,259
    edited 2011-08-11 15:11
    Sure Peter, then just press the UNDO button... :)
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-08-11 15:56
    agimuhing wrote: »
    my multimeter shows infinite resistance both ways the capacitor is connected.

    Depending on the impedance of your meter, and if the "100" on the device means 100 microfarad, you may have to keep it connected a while before you start seeing anything.

    An analog meter is the better tool for this. You can still find them, especially used.
    -- Gordon
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