Capacitors at RF

Gentlemen,

Does anyone know what frequency capacitors are generally measured at? I'm finding correlations at 3Mhz with rated values, but that strikes me as on the low side.

CD

Reply to
Cursitor Doom
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It's a silly question. The size of the capacitor does come into it, and the way they are constructed.

You measure at a frequency that puts enough current through the capacitor to be reasonably easy to measure, but not enough to cook it.

Capacitor data sheets do tend to include useful information - there's not a lot of point trying to measure capacitance at a frequency where the capacitor looks resistive or inductive.

You aren't going to measure the capacitance of a 10pF RF capacitor at the frequency you'd use to measure 10,000uF electolytic.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

I don't think there is a 'generally'. Every manufacturer does whatever pleases them. What makes you think it's 3MHz?

Jeroen Belleman

Reply to
Jeroen Belleman

Because at that frequency, my VNA's reading of the capacitance value agrees with that printed on the cap. And it's a fairly narrow range, too. Go too far away from 3Mhz and the measured value strays markedly.

Reply to
Cursitor Doom

You either didn't read the question, or understand it. Seems a common problem you have lately, Bill.

Reply to
Cursitor Doom

Cursitor Doom puked a pile of crap :

** FFS say what sort of cap it is f*****ad.

..... Phil

Reply to
Phil Allison

On Sun, 17 Jan 2021 03:39:20 -0800 (PST), Bill Sloman wrote:e.

A 10,000uF electro would be measured at 100kHz. I want to know what a capfor RF in the pF range would be measured at. Different thing altogether.

Reply to
Cursitor Doom

Cursitor Doom puked a pile of vomit:

============================

** You did not post a question.

** It contained no information or intelligence

So exactly like you - f*****ad.

Reply to
Phil Allison

Well, there's tolerances to keep in mind, and maybe setup parasitics. What kind of capacitor are we talking of here? It doesn't sound like it's an RF-worthy kind.

Jeroen Belleman

P.S. Would you please stop trolling Mr. Sloman? It's a waste of time.

Reply to
Jeroen Belleman

Cursitor Doom puked hi dinner up :

=============================

** Like HELL it would - you lying ass.
** Typical LCR bridges work at audio frequencies for C measurement. Fuck knows what weird crap you are up to - dickwad.

..... Phil

Reply to
Phil Allison

e frequency you'd use to measure 10,000uF electolytic.

If it was designed for use as a reservoir capacitor in a switching power su pply - those do tend to have relatively low equivalent series resistance.

fferent thing altogether.

So why didn't you say so when you posted your original question? No matter how carefully I read your original post, I can't find any reference to a c apacitor in the pF range, or that you intended it for use at RF (which is s till pretty unspecific. 100kHz (and lower) has been used for radio-frequenc y transmissions.

Maybe you could take more care about telling us what you want to know?

--
Bill Sloman, Sydney
Reply to
Bill Sloman

===================

** You bet.

Few years back I challenged a usenet poster on his numbers for electro self resonance frequencies as published in a tech magazine under his name. They were all WAY low - like 10 times under.

He pretty much refused to reveal any details of his his test set up.

Finally he admitted he measured the output level from a function gen at it terminals with a scope, while the C on test was attached at the end of a pair of half meter long leads.

FFS.

..... Phil

Reply to
Phil Allison

I measured ESL of some radial-leaded electrolytics some years ago and I was really surprised to find values in the 5nH ballpark, much lower than I expected. It's in the same ballpark as disc ceramic 'RF' capacitors, when those were still a thing.Axial- leaded caps were in the 100nH ballpark, much worse.

Jeroen Belleman

Reply to
Jeroen Belleman

Wow, you Australian trolls sure know how to back each other up! :-D

Reply to
Cursitor Doom

Your attitude problem is surfacing again, Phil. Seems to be a common problem with Australians like you and old Bill. You're at the bottom of the world and everyone ignores you. You read the international news and Australia plays no part in any of it. Everytyhing happens in the US, the UK, Russia and China. You feel left out and affronted, so you throw all your toys out of the pram to get attention like some obnoxious child. Ever heard of Rod Speed? Another notorious Australian Usenet troll. The three of you probably contribute to at least 10% of the garbage appearing on the internet worldwide in any given year. Waste of space the lot of you.

Reply to
Cursitor Doom

Very wise of him. He clearly knew you'd be of no use whatsoever and no time should be wasted on you.

Reply to
Cursitor Doom

There'd be no point in doing this with any other kind. And yes, I am well aware of the importance of eliminating the parasitics and observe best practice in this regard.

Reply to
Cursitor Doom

Are you sure that you're not seeing resonances with the connecting leads?

In the tube era, capacitors acted up because of stray inductnces in the connections. In the same way, inductors acted up because of internal stray capacitances. The high impedance levels and the large size (by current standards) of the components added to the difficulties.

--

-TV
Reply to
Tauno Voipio

None that Cursitor Doom knows anything about

Or so he likes to claim. He does seem to have a high capacity for self-delusion.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

We do seem to be intolerant of useless twits who are convinced of their own expertise. The UK did export a lot of them to Australia, and Australians do seem to have developed an effective coping mechanism. It wasn't taught in schools when I was a kid- some of my more useless teachers were UK rejects - but more technically demanding environments provide frequent demonstrations of the technique in action.

None that Cursitor Doom is aware of.

Not quite. But Russian Today and ZeroHedge don't spend time on anything outside their target audience's rather narrow interests.

The most recent reference to him is dated 2004 and asks whatever happened to him. Not somebody I ever ran into

We clearly couldn't deliver the right-wing conspiracy nonsense to which Cursitor Doom is addicted. His tastes are specialised to the point of being peculiar.

Of course Australia did invent the WiFi system which Cursitor Doom and every other keyboard warrior relies on, but that's electronics and he doesn't know anything about that.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

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