Need help about capacitors

Discussion in 'General Electronics Chat' started by Formingus, Mar 16, 2015.

  1. Formingus

    Thread Starter Member

    Nov 19, 2014
    37
    0
    There are few different capacitors on most of PCB.
    I read somewhere that 470uf with 35v capacitor should have no more than 0.09 ohms and while we measuring them with ESR meter if they pass limit they are almost open circuit.
    Its same calculation for other capacitors but when they have different values we need to know their values so we can know if they are leak or defective ones.

    Is there any specific table, method, software or way to know exactly what values need to have aluminium, colored, electrolytic, smd, smt capacitors and so on ?

    Mentioned for example electrolytic ones that have uF and Volt written on them but we need to know their OHM values too.
    So when i see part number like 104 on capacitor or some other info to know exactly what values they need to have so after measuring i can recognize leak or defective ones.
    Found some tables o SW like OHM Laws but get confused with allot of them
    Will be highly appreciated if someone lead me to easy and correct way.

    Thanks in advance
     
    Last edited: Mar 16, 2015
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
    2,373
    There is ESR, Equivalent Series Resistance, which is the AC impedance of the capacitor when used at a particular frequency and includes the resistance of the dielectric material.
    Many manufacturers will issue a ESR value, particularly for electrolytics where the value is relatively higher that other types.
    Max.
     
  3. Formingus

    Thread Starter Member

    Nov 19, 2014
    37
    0
    Let see did i get point
    Depend of manufacture values are differen ?
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    you have to read the specs for the esr value, they arent printed on the caps. the chemical mix and age of the caps determines the esr. as the caps age, they dry out, or change their chemical makeup, which increases the esr, causing heating, which causes them to age faster.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,389
    1,605
    Yes, each and every capacitor is different, best to check the manufacturer's spec on the specfic deviced you are using.

    Keep in mind if the ESR was something wonderful the manufacturer would be excited to place it on his spec sheet. When ESR is importaint to your design and the data is missing look for another part.
     
  6. Formingus

    Thread Starter Member

    Nov 19, 2014
    37
    0
    Guys thak you for all replays
    but sometimes there are allot of them to check for ex: see this PCB
    How can i get all those values ? Some of them does have no number at all like brown ones and so on


    Regards
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    Give up now. I'm sad to say it, but that's what I'd do.
     
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