Subject: Re: AN: New Logic Analyzer, 500MHz, $166
Date: Sun, 17 Nov 2002 20:12:01 -0000
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NNTP-Posting-Date: Sun, 17 Nov 2002 20:11:31 +0000 (UTC)
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John Jardine wrote
> Offhand, as there is stray capacitance between the connecting wires, I would
> have thought it better if the wires are looked at as a distributed
> transmission line. In which case at 500Meg the wires may have a simple
> 'resistive' impedance of a few hundred ohms. But of course ... the
> 100kohms//10p meter input impedance is in no way going to terminate that
> line, which still makes the makers claim of a 500Mbit/S measurement,
We definitely take measurements at 500MHz :-). As for the input
circuit, there is also a 1K in series with the 100kohms//10pF, as
in the equivalent high-price circuits.
And the wires should be kept as short as possible (some customers
want even longer wires). 30cm is a balance of various customer
requirements, and probably too long. We will shorten it to 20cm
for the next build.
For high-speed measurements, a simple vise allows the customer to
shorten the leads right down to a few cm.