[SI-LIST] Re: To measure impedance of a capacitor using VNA
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: antokdavis@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 12 Mar 2014 08:53:58 -0400
Hi Anto,
Fair question, but for most practical situations, you dont need to worry.
Even with very simple instrumentation, like a VNA created around a little
USB-powered oscilloscope with an arbitrary waveform analyzer), the
Two-port shunt-through measurement will be reasonably good up to
at least a kohm impedance magnitude. Professional network analyzers
have better resolution and you get reasonable result at least up to ten
kohms. For a 0.1uF capacitor this means you dont need to worry about
this potential problem unless you want to measure the impedance at
frequencies with single digits or below. If that was the case, you can
use either traditional impedance bridges or just use the same two-port
setup but switch to series-through connection.
Best regards,
Istvan Novak
Oracle
On 3/12/2014 7:12 AM, Anto Davis wrote:
> Hi,
> I am trying to get the impedance plot of a 0.1uF capacitor (using VNA),
> which has ESL and ESR associated with it. The frequeuncy response should be
> a V curve. From the book, Frequency Domain Characterization of PDN by
> Istvan Novak (ch-5) I realized that two port measurements are better
> (measuring Z12 or S12) when Z << 50 ohms.
> But for a single capacitor, how to get the V curve? If I connect it to
> measure as Z12, I can measure it correctly for frequencies where Z<<50 ohms
> only?
>
> Thanks,
> Anto
>
>
>
>
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