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| Distinguishing ceramic from film capacitors electrically? |
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| David Hess:
--- Quote from: mcovington on December 10, 2019, 10:26:43 pm ---How do you know? --- End quote --- I can tell from the form factor and size for a 0.1 microfarad part. A disc ceramic or film would be larger at that value. The film example shown is a polyester stacked metal film capacitor; they work fine in place of ceramic capacitors in decoupling and filtering applications. Both of those are constructed by welding leads to a common rectangular surface mount part and then dipping it in epoxy. If you heat the part and twist the leads, they will separate exposing the inside construction. |
| MT:
I wonder how much of fan, harddisk etc vibrations creeps into pow supply via SMT decoupling cap's? Any studies around? |
| T3sl4co1l:
"A5K" sounds familiar and ceramicy, though I don't know what it means (it's not a type code). The shape suggests some odd ceramic, but they could be stacked film as well. The tempco is definitely(?) too low for X7R or worse. If they're PET, they'll have somewhat higher losses than PP or C0G, which you might perform an experiment on. You'd do that by setting up a few watts from a signal generator or oscillator, and tune a resonant tank to it. Most of the losses will probably be in the inductor, but there should be enough that you can feel some in the cap, and perhaps compare to known types. --- Quote from: MT on December 11, 2019, 01:15:32 am ---I wonder how much of fan, harddisk etc vibrations creeps into pow supply via SMT decoupling cap's? Any studies around? --- End quote --- A few mV, give or take. Yes, search for "ceramic capacitor microphonic". Tim |
| MT:
--- Quote from: T3sl4co1l on December 11, 2019, 01:29:38 am ---A few mV, give or take. Yes, search for "ceramic capacitor microphonic". Tim --- End quote --- I im aware of the standard piezo microphonics what im wondered about was "studies" made on fans and hardisk vibrations. Surely this depends om cap material, mounting material PCB, distance of vib source, microphonic bandwidth, resonant frequencies of/on the board, etc, etc, etc. Even in Daves EVVBLOG some time ago in which he taps the front of various scopes made a HUGHE difference and not some mV! |
| bob91343:
I would guess A5K means 5 pF and 10% tolerance. Dunno about the A. But that disagrees with the other side. Still, the K tells me 10%. I recall the days with the six or three painted dots on mica capacitors. I have some and not only can the coding be confusing but the old paint changes color. |
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