OT: Network Cable Tester

[drew einhorn]

On Thu, Sep 24, 2009 at 3:44 PM, David Curtis <dcurtis at uniserve.com> wrote:
> On Thu, 24 Sep 2009 15:04:23 -0600
> drew einhorn <drew.einhorn at gmail.com> wrote:
>
>> On Thu, Sep 24, 2009 at 1:37 PM, Roger Neth Jr <baypos at gmail.com>
>> wrote:
>> > I have used a Fluke 620 for 8 years and works great for what your
>> > needs are, look on ebay also.
>>
>> Definitely can't afford a new one.
>> Might be able to afford a used one on ebay.
>>

Hmm.  The more I look at it, the more I think it's worth it.

>> Looking at the specs.  How do they do that?  I can see some of it.
>> But, without something connected at the far end, how do they tell
>> there isn't an open circuit at the connector on the far end of the
>> cable?
>
> http://en.wikipedia.org/wiki/Time_domain_reflectometry
>
> and
>
> http://en.wikipedia.org/wiki/Time-domain_reflectometer
>
> Not exactly sure what improvements have been made over the years, but
> in the late '90s we would send PCBs to get 'TDR' tested to measure the
> impedance of certain copper traces that carried either high frequency
> signals or were part of differential circuits. Same principles apply.
>

That's what I was thinking in general, but had no idea the resolution was good
enough to see that the connector is wired correctly.  Especially,
without needing
to plug in some kind of terminator.  I thought it was just good enough
to see how
far down the cable the faults are.

It almost sounds like it has too be able to detect the color of the
insulation, and
sense pin numbers for some of its tests.

There's definitely more here than I understand.

I need to go download a manual and get a better idea idea about exactly
what it can and cannot do.

-- 
Drew Einhorn