Laptop-based TDR meter

[Joerg]

Hello Folks,

A while ago some of us were pondering a light-weight TDR that is small
and can be hooked up to USB. Well, in the last issue of the
"IEEE-Institute" one was presented and it's from this company:

http://www.ecadusa.com/tdr3127.htm

Ok, it's the old PCMCIA but it will be only a small step to swing that
to USB if the market is there.

 

[Joerg]

Not bad... I wonder what the cost is?

I'm about to lug a spectrum analyzer over to our annex... you're up for
providing design advice on that USB-based version, right?

I am not an expert on that but once I was surprised how easy that is if
you use "take-and-bake" parts and firmware. Took a regular Cypress PSoC
and their canned USB routines. IIRC the programming part required about
20 minutes.

 

[Joerg]

I wonder about the output drive requirements for some applications given
the PCMCIA card's power supply limitations. With a USB device, you could
incorporate an (optional) external power supply.

One option would be to use a cap to store enough energy for "the mother
of all pulses"

Given the quoted range they almost have to.

 

[Joerg]

PCMCIA? How quaint.

Surprisingly even my newest laptop still has one slot.

They avoid specifying time resolution, and the 6.4 Gs/s sample rate is
fiction. The time step is 1 ns (typ?) but the actual measurement
resolution is unknown.

It's probably the usual "equivalent time sampling" and they state one
inch resolution. That won't be good enough for a circuit board but their
market is cables.

Looks OK for single-ended cables; way too slow for PC boards.

Hyperlabs makes a fast USB TDR, but it's expensive.

No idea what theirs costs either.

 

[Spehro Pefhany]

Surprisingly even my newest laptop still has one slot.

You sure? Most have Express Card these days, IME, and they look almost
the same from the outside. They're supposed to be able to transfer
data much faster than PCMCIA/PC-card.

It's probably the usual "equivalent time sampling" and they state one
inch resolution. That won't be good enough for a circuit board but their
market is cables.



No idea what theirs costs either.

Best regards,
Spehro Pefhany

 

[Joerg]

You sure? Most have Express Card these days, IME, and they look almost
the same from the outside. They're supposed to be able to transfer
data much faster than PCMCIA/PC-card.

Me sure

It's a Twinhead Durabook and I purposely selected that one because it's
ruggedized and carries legacy ports such as RS232. Sez PCMCIA and
PC-Card in the specs. Never used the PCMCIA slot so far but the RS232, a
lot.

[...]

 

[Joerg]

The 1" resolution isn't compatible with a 1 ns risetime step. These
people are confused.

Don't know but they better be able to back that up because they work for
NASA etc. Maybe they get to 1" by micro-scooting and finding the
correlation peak of an abnormality.

 

[Jamie]

I made a mistake and bought a "gaming" laptop towards the beginning of this
year. It is fast with a great graphics card, but doesn't have a docking
station nor an RS-232 port.

I replaced it with a used HP Compaq nw8440
(http://h18000.www1.hp.com/products/quickspecs/12449_div/12449_div.HTML) for
$600 via eBay. 2.16GHz CPU, 2GB RAM, 1920x1200 15.4" (!) display, docking
port, and RS-232. It's a beautiful thing to behold, I tell you -- especially
given the price! I had assumed that when HP acquired Compaq all their
"business" laptops would go away and therefore HP was only making cheesy
low-end laptops... nice to have been wrong there...

---Joel

Nice laptop, maybe I'll buy one as a back up.
Recently got a Panasonic Tough Book because I needed the
Serial port and Windows XP PRO SP2. It also offers all kinds of
other goodies. I noticed after browsing around it seems the
Panasonic's are cheaper than that HP how ever, HP seems to be
more popular. Not saying they're any better.

I also have Toshiba Satellite Pro model which has the
serial port and a printer port along with a built in floppy,
USB,Firewire, 10/100 Enet, 802.. Built in wireless, IR port
which I really like to transport data with devices just sitting
beside it.. And the usual stuff like DVD/CD burner etc...That was a
computer show grabby for $250..




http://webpages.charter.net/jamie_5"