Hi,
I need to have non-inductive capacitors (100nf) (a datasheet told me to 
) But I'm not sure how to find one. Do you have an idea how I could find one or have a specific model?
Thanks!
Polypropylene Capacitor
Mylar Film Capacitor
Any thing can be inductive. It is just a matter of different degrees of inductance.
Generally, electrolytic capacitors, or paper capacitors, or film capacitors on a wound-up construction, are fairly inductive. Most "non-inductive" capacitors are stacked, not wound.
If datasheet has the "self-resonant frequency" this is a useful guide to how inductive a capacitor is.
1
L = --------------------------
C * (2pifreq)^2
That page has a paragraph with bizarre statements like I've never seen:
Uses of Noninductive Capacitors
There are a varied set of applications for noninductive, coated capacitors. They make excellent blocking and coupling devices, are efficient by-passers and circuit filter elements and also work well in circuit timing. Subsequent uses are found in audio equipment, sound production devices and telephony. They act as high-power, high-voltage resistors, "snubber" resistors, used in railway technologies and in discharge applications. Ceramic carbon noninductive capacitors make resistors which are 100 percent active, as described by Hill Tech.
DUH? Can someone explain this - "They act as high-power, high-voltage resistors, "snubber" resistors, used in railway technologies and in discharge applications. Ceramic carbon noninductive capacitors make resistors which are 100 percent active".
I see nothing about this on the Hill Tech page cited.
http://www.hilltech.com/products/power_components/p_resistors_hi.html
Mmmm, sounds wierd. Perhaps the 'coating' is sometimes a resistance coating. That would make a nice snubber component.
Perhaps they mean non-resonant rather than non-inductive.
DUH?
The 1st half of the paragraph is sensible.
I'd like to propose a moratorium on LMGTFY. While funny five years ago, this is basically a sarcastic way of saying "look it up yourself." I can't speak for the OP, but the one time in my life I've been the recipient of such an answer, I would have rather there had just been no reply. Furthermore, in a good half the cases where I've personally seen it used on others, the first page contained perhaps a definition, but very little useful information beyond the obvious. As if maybe the Googler didn't even look at the results, and just assumed the answer to the painfully obvious query would be prominent. This may be just my own experience vs. representative samples, I understand...
As a positive alternative, I think the OP's question can be easily expanded beyond "what's that?" to "what is considered low-enough?" or "what am I getting myself into that I may not know enough to ask about in advance?" At least here in Arduino land, when someone asks a question like this, there's often a good page or two of replies with thoughtful and though-provoking answers that I may never have pondered myself had I not stumbled upon the post. In other words, a simple question contributed to the common good -- at least for me.
So, just a thought. If this is not a popular opinion, I'm willing to be overruled.
I didn't know squat about Arduino, electronics, and very little about programming a few months ago, but since I keep Google in business with all the searches I do, I tend to search for a few hours before I give up. One example, for me, is this thread. I didn't know what a "non-inductive" capacitor was. But after just 5 minutes of Google, I know what they are and how to look for them if a situation arises.
I didn't mean to be rude to get anyone mad. For that I apologize. But, if it wasn't for Google, I would be sitting in front a TV, watching Oprah...
Well the reality of the issue is that there is no such thing as a real "non-inductive capacitor", that's just a marketing term implying the suitablity of a specific capacitor for use in very high frequency applications. When you get up into the VHF/UHF/microwave frequencies every component (including it's lead length) and indeed even PCB circuit traces has some amount of inductance and capacitance which has to be accounted for in the design of circuitry operating at those frequencies. So certainly not every .1ufd cap is identical in it's inherent inductive value, but that does not mean that it's an important parameter for the specfic circuit one is working with. Same applies to resistors, where 'non-inductive' resistors are important for RF circuitry where having a flat frequency response can be important such that wire wound power resistors are not a good choice.
Thanks for your replies.
First of all, of course I googled, of course I found thousands of sites. BUT, my questions was not, "what is it?" but, how do I find one. Probably I should have been more clear about that, but if I google it, I get definitions, not parts I could buy. If I enter it in ebay, i get nothing. At the moment, to me it looks like I have to look for capacitors, then open their datasheet and look for the inductance. So I hoped, someone could probably point out, that all "xy" capacitors, or all with a X in the beginning or something like that could help me find out. Once again, I know what it is and I googled it, I was just looking for one especially.
Oh and to all the guys out there who keep screaming "you could have just googled that", please note; for us non-english speaking people, it is MUCH more an effort to write a correct question into a forum than just google it. Think about that.
someone could probably point out, that all "xy" capacitors
I don't know if that will exist, as a capacitor's inductance / inductiviness has a lot more to do with its construction than anything else.
Technically you're correct, but in practice you can just use a ceramic radial mounted as close as possible to the part, and with the shortest leads possible. AFAIK, that's about as low-inductance as it gets short of surface mount parts, and I'm going to assume that's out of the question here. I use the little TDK blue ceramics from DigiKey for all my through-hole decoupling.
The PDF linked above has a really good explanation of this, and as pointed out before, it may be helpful to parallel a large(r) electrolytic to catch higher current loads.
BTW, thanks for the understanding on the LMGTFY thing. I don't mean to lecture, just trying to add perspective and keep up the supportive community here.
I need to have non-inductive capacitors (100nf) (a datasheet told me to )
After all the comments here, I'm curious as what datasheet you were looking at.
????
I'm curious as what datasheet you were looking at.
It is not uncommon for a high speed digital circuit to ask for that. This is an area where smd parts have considerable advantage over through-hole parts.
Bump
I am also looking for this (100nF non inductive specifically). A bit disappointed that the OP didn't get the tips he needed, which basically was how to determine whether a capacitor is "non-inductive" or not, when you're shopping for one. Most vendors I've seen makes no mention of it...
A bit disappointed that the OP didn't get the tips he needed, which basically was how to determine whether a capacitor is "non-inductive" or not, when you're shopping for one.
But he did. He was told there was nothing that would tell you apart from the data sheet.
He also got told there is no such thing, it is a matter of degree.
So if you have a specific request then post the data sheet and we will see what is suitable.
Note it is common for data sheets and application notes to request impossible components / decoupling requirements and defend it by saying this is an ideal situation to fully meet the specification. It is up to the engineer to come up with a practical circuit.
Grumpy_Mike:
But he did. He was told there was nothing that would tell you apart from the data sheet.
Ok, sorry, I mistook that for an opinion and not a definitive answer... Anyway, do you mean the datasheet for each and every capacitor, or the datasheet for the component I working on that asked for it? In the latter case the datasheet is: https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf.
Although, I've come to suspect that the pcb my L298n chip come attached to already have the capacitors (no datasheet for the pcb though, but I'm pretty sure), so probably won't need one after all... It looks like this:
It got 8 diodes and two capacitors that sort of add up with the datasheet schematic, and I assume they're not there just by share accident
I guess if you're sure that there's no general knowledge to derive from this (with respect to finding one on your own), then I guess we could lay it all to rest, again... Unless you're still willing to explain how you would go about finding one, for that component, if indeed I did need it. I wouldn't mind, if there anything to learn, but it's not super important (I hope) anymore... 
do you mean the datasheet for each and every capacitor,
Yes until you find one that will do.
Unless you're still willing to explain how you would go about finding one, for that component, if indeed I did need it.
Well if I needed one then I would know what sort of inductance was required and then I would ask. Either the buyer in the company I worked for or the sales rep for a capacitor company. Failing that I would ask one of the major distributors. The trick is that you have to sound like you know what you are talking about.
no datasheet for the pcb though,
No you don't get specs like this for a PCB.
In general surface mount ceramic capacitors are quite low on inductance. Some electrolytic capacitors have both clockwise and anti clockwise winding in their construction to cancel out the inductance.
For a L298n the type of capacitor required is nothing out of the ordinary.