Capacitor Question

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Capacitor Question

Postby vez on Tue Nov 06, 2012 12:51 am

Im testing .02 caps on a ohm meter destined for my guitar and some make the needle jump a little bit more than others.
Is this meaningful?
Thanks
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Re: Capacitor Question

Postby Unit_1 on Tue Nov 06, 2012 4:38 am

hey vez

ohm meter is for checking resistance

you will get no meaningful data from using it on a capacitor

what you are seeing is the cap getting a slight charge from the battery in the ohm meter as the meter slowly goes insane from being hooked to a cap :lol:
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Re: Capacitor Question

Postby vez on Tue Nov 06, 2012 6:37 am

Unit_1 wrote:hey vez
ohm meter is for checking resistance
you will get no meaningful data from using it on a capacitor
what you are seeing is the cap getting a slight charge from the battery in the ohm meter as the meter slowly goes insane from being hooked to a cap :lol:

Unit_one, my California compadre! Thanks for the reply.
Yes I know, the OHM meter is a DC source but as they charge the needle jumps from infinity slightly showing a resistance for a fraction of a sec. Im just wondering why some caps make the needle jump a little more than others bearing that they are all the same value, in this case .02 mf.
I'm curious.
BTW any earthquakes out there lately? We just have a hurricane out here :lol:
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Re: Capacitor Question

Postby Unit_1 on Tue Nov 06, 2012 7:13 am

vez, my eastcoaster amigo!

yeah, as a matter of fact we had a 3.9 a couple daze b4 that bitch sandy hit the beaches!!

i was in bed and knew it was an earthquake and didn't even twitch.... i do remember muttering "-f-u-"

if you don't have to grab onto the bed with both hands to keep from flying off, then it's nothing to get excited about!!!!! :mrgreen:

caps should have eXtremely low resistance - and hard to measure with an ohm meter because of the 'getting charged by the battery' thing

here's more than any sane person would ever want to know about caps, and resistance and leakage and other stuff i almost comprehend!!!!!!

http://conradhoffman.com/capchecktut.htm

i think this guy may very well be one of those e-o-lectronic geniuses....

btw, this is my vintage cap checker:

Image

so .02 huh? care for an astron paper in oil, or perhaps a super rare and reliable cde greenie? i got pounds of 'em..... :shhh:

Image
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The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

Asimov:Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today — but the core of science fiction, its essence, the concept around which it revolves, has become crucial to our salvation if we are to be saved at all.
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Re: Capacitor Question

Postby vez on Wed Nov 07, 2012 8:02 pm

Oh man that thing is great! Where did you find it? :thumbsup:
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Re: Capacitor Question

Postby Unit_1 on Wed Nov 07, 2012 8:12 pm

vez wrote:Oh man that thing is great! Where did you find it? :thumbsup:


why eBay, but of course. they have them come up all the time. anywhere from $180 to about $300. you just gotta be sure to get a T0-6A, not a T0-6 or before because the caps on those leak. yup, the tester for leaky caps had leaky caps. this one is supposed to have leak proof caps.

and like you can do it yourself with a transformer, recitfier, a variac and a amp meter. you just dial in the right voltage, connect the cap to the DC and put the meter in-circuit after that to ground and measure to see if there's any DC amperage. if so, the cap is leaky.

but like, what a hassle..... so i bought the tester. and it looks so cool.....
Image
The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

Asimov:Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today — but the core of science fiction, its essence, the concept around which it revolves, has become crucial to our salvation if we are to be saved at all.
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Re: Capacitor Question

Postby demonufo on Thu Nov 08, 2012 7:37 am

On very large capacitors, using an ohm-meter (usually on it's highest settings, and analogue is better here...DON'T use meggers unless you know them to be below the rated voltage of the capacitor)to see how long the capacitor takes to charge can show some sort of degree of the condition of the capacitor, but it takes comparison of a known good capacitor of the same type, value, and voltage rating, and a good deal of experience to make a judgement call. It still won't really tell you anywhere near as much as testing for ESR, insulation resistance (at it's rated voltage - something those Sprague units are PERFECT for...) and leakage currents, but it can help weed out the worst of them.

However, I really wouldn't recommend laying any faith in this sort of test.

On signal caps, it's useless. Needs to be larger electrolytics really, before you'll begin to see anything useful.


Edit: I should add, if anybody is crazy enough to use a megger on a capacitor, you may just want to think about shorting those capacitor leads afterwards before you touch them and give yourself a nasty shock. :Zap: :Zap: :Zap: :Zap: :Zap:
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