[time-nuts] Prologix GPIB-USB vs. GPIB-LAN vs. NI was: AW: Prologix GPIB-USB vs. GPIB-LAN

John Ackermann N8UR jra at febo.com
Mon Jul 6 12:37:09 UTC 2009


A bit further to Ulrich's point... one area where I had some problems 
using serial/gpib converters in the old days, and I think that at least 
early versions of the Prologix USB unit suffered from, is talking to 
multiple instruments off the same GPIB controller.  I never found a 
satisfactory way to accomplish that with anything other than a "real" 
GPIB card.  (But Prologix may have addressed this by now.)

I think GPIB applications break down into a couple of categories:  (a) 
simple trigger-then-read from a single instrument, which is what most of 
us do most of the time, and (b) multi-instrument control.  The second 
case is a lot harder, particularly if you need to use SRQ and other 
out-of-band commands.

Of course, an alternative is to assign one USB or LAN GPIB unit to each 
instrument, but that gets expensive.

John
----

Ulrich Bangert wrote:
> Gents,
> 
> as you know I have tried in my utility EZGPIB to supply the user with high
> level functions for data communications which keep him away from the low
> level tasks of direct communication with the interface. Since EZGPIB not
> only supports the Prologix products (USB & LAN) but also GPIB32.DLL based
> products (i.e. the complete line of NI GPIB interfaces) a script written in
> EZGPIB is independent from a certain manufacturer to a high degree. 
> 
> That is the point that I wanted to add to the current discussion.
> 
> Please allow me to note that this independence has its limits that I just
> happened to come across. I had tried to run a script for my SR620 counter
> which was set to a gate time of 100 s. The script was a quick and dirty one
> and set the timeout for GPIB communications to 120 s so that there was
> enough time for the counter to answer, even if the data was read immediatly
> after tze start of a new measurement. This script would not run ok on my
> Prologix GPIB-ETHERNET interface although I was sure that is was ok when I
> wrote it. 
> 
> It took me some time to realize that I was fooling myself: I had written the
> script with my NI interface which's DLL allows for some decades of magnitude
> of timeouts while the Prologix provide a maximum timeout of 4000 ms. That
> means: Some things cannot translated 1:1 between different manufactures. I
> changed the script so that the conunter's status byte was read once a second
> and the "data valid bit" is detected in the status byte. Then the counter's
> result is read. This of course run ok (also on NI hardware). I will include
> a warning in the manual of EZGPIB.




More information about the time-nuts mailing list