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

[Chuck Harris]

Hi John,


> 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.

With the loading limits on most small microprocessors, this seems reasonable.

And I am glad to hear that it is possible.  It extends the use of the
Prologix from one adapter/one box model, to being able to run something
like an 8505A network analyzer where there are 3 or 4 boxes all on the bus.

I waited for version 5.00, with its multi address capability, because I
had envisioned using it one day to add automation to my 8505A system.

>> 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.

Abdul has been great with his support.  I have no complaints.  I would have
some, if I didn't jump into this deal already knowing pretty well the potential
caveats of the design.

A given instrument's support of the IEEE-488 standard is a little different
from a competitor's support of NI's house brand standard.  Kind of like
trying to be a windows compatible operating system when microsoft only
wants you to buy its operating system.

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

Certainly not.  But how many use it that way?  It is generally used as
a single controller with multiple talker/listeners, working sequentially
when addressed by the controller.

> 
>> 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?

It was the tone of your suggestion that everyone that buys a unit and finds
out that it doesn't work on such-and-such an instrument should be given his
money back, and sent away.

I am all in favor of a product that has known design constraints that keep
its price low.  I bought this adapter knowing that was true.  It would be
nice, though, to have the option of having the same design available with
true 488 drivers.  I think that capability would smoke out a few more
customers at very little extra cost.

> 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.

That is what I believed to be true.  You have said nothing to imply any
other relationship.

-Chuck Harris