Higher or Lower Tolerance Ratings for Caps?

Discussion in 'General Electronics Chat' started by TheLaw, Sep 2, 2010.

  1. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Hello folks,

    Better now than never I suppose...So, in general, is it better for a capacitor to have a tolerance of +/- 1% or +/- 5% or +/- 20%. What does tolerance really mean to me and to the application?

    Thanks.
     
  2. Ghar

    Active Member

    Mar 8, 2010
    655
    72
    It could mean nothing, it depends on the application!

    If you're just using it for smoothing and guesstimated the value as "good enough" then 20% either way won't hurt you.

    Basically the question is, do you care if your capacitance is off from the value you picked?

    If you're trying to make an oscillator and the capacitor specifies your frequency then you probably want a precision capacitor with low temperature coefficient and you'd get the best you can.

    Also keep in mind that capacitance varies with applied voltage (can be 50% decrease in some varieties!) and temperature (another 20%!).

    If you're designing a sharp filter and want specific frequencies you go for a good tolerance.

    The idea I'd go with is this:
    Did you calculate a capacitor or just picked one out of thin air?
    If thin air, it doesn't matter.

    If you picked one, what is the effect of a capacitor being a different value and do you care?
     
  3. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Well I am making a very simple circuit that uses a MAX232 so I can cost-effectively connect my homemade Arduino board to my PC without having to buy a $20 converter board.

    I need 4 1uF caps. Ceramic would be the type. I just looked up the schematic. I am not sure exactly what they are doing because I don't really know how the MAX232 works internally.

    Well, for future reference....

    Does tolerance mean how close its actual characteristics are to its specifications or does it mean how much more capacitance it can take outside of its spec before it blows up?

    Thanks alot for the detailed response.
     
  4. Ghar

    Active Member

    Mar 8, 2010
    655
    72
    It's how far off it is from the specifications.

    A +/-20% 100uF capacitor might be anywhere from 80 uF to 120 uF

    Tolerance works like this in general.
     
  5. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Okay thanks. I never really considered tolerance, but I saw tolerance on Mouser today and it reminded me that I still have no idea the exact definition of it.
     
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