[time-nuts] OT: Prologix GPIB and HP3478A...The Answer!

John Miles jmiles at pop.net
Wed Nov 28 14:31:35 EST 2007

> Hi John,
> I agree in part.
> If it is known that certain GPIB instruments are not supportable,
> then it is essential to have that documented fact easily available to
> the buyer.  Thus far, the Prologix website, and documentation, make no
> mention of any possible limitations, or deficiencies.  [For instance, it
> clearly cannot support the maximum defined GPIB system, or cable lengths.
> That should have been mentioned.]

Agreed, documenting this sort of limitation is pretty important, now that
it's known.  That said, his intent has always been one dongle per
instrument, plugged directly into the back without any cables at all.  The
first few generations of the board used a DIP switch to set a hardwired
address, in fact.

I have run mine with at least a half-dozen daisy-chained instruments on
20-30 feet of cabling with no problem at all.  Some of the 8650-series
signal generators cause loading problems when they're powered off, but
that's true with the NI boards as well.

> I would be angry, except that I already knew that the design had a major
> short cut in it before I bought my Prologix.  If you recall, I addressed
> that issue many months back on this forum.

If you want 'anger', try spending time supporting other boards, especially
the off-brands that claim to be NI488.2-compatible.  Anger is only the
second or third stage of the grief that process brings.

And GPIB itself is not exactly a textbook example of how to design a
multiuser bus.

> I bought my Prologix controller based on the good reports that all of
> you guys posted.  And the need to control a single device, a Tektronix
> 7854.  It will do that, so I am satisfied.
> The "Go away kid, you bother me!" approach won't win over many
> customers.

I'm sorry; who said that?

I need to clarify that I've helped Abdul with some testing now and again,
but have absolutely no other business relationship with him, other than the
fact that I happen to live in the same area, and regularly let him (and
pretty much anyone else who asks) drop by to use my test gear.

-- john, KE5FX

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