Performance of GPIB (with Tectronix scope)

Question

I have an ICS Electronics GPIB card and I'm using the Quick Basic
libraries that came with it to code a program that captures a section
of the displayed trace. The scope is a Tectronix TDS-210.
The first version of the program used the RS-232 port and I was
capturing 512 samples of the captured trace (out of a possible 2500
points). I am capturing thousands of traces in a sequential manner.
The throughput using the RS232 port was about 1 capture per second.
With the new code for the GPIB port, I can capture about 3 traces per
second. I was expecting a MUCH higher capture rate given that GPIB
has a stated transfer rate of at least 200k bytes per second.
So, my question is this: Is it typical that certain GPIB cards or
har
dware has effective transfer rates that are much below GPIB spec,
or is this a case where the command or instruction-processing within
the device (TDS-210 in this case) is incredibly slow?

Answer 1

FYI - re Tektronix 'Wavestar' - I have used this on Tek TDS/THS scopes,
and as far as I can see it is not 'built for speed'. It does a credible
job of downloading and archiving scope files, once one has deciphered the
cryptic interface. But as far as automating rapid i/o, I dont think it
can beat hand-coded software, BASIC or otherwise.
IMLE, data transfer specs are never really realized in real world apps
no matter what the application:
VME/VXI/PCI/GPIB/IEEE1394/RS232/USB1/USB2/IEEE802.11 etc.
fwiw, I would agree a dedicated NI PCI scopecard would most likely achieve the
fastest capture rate, but would not be less expensive than a TDS2xx/3xx scope,
esp when adding in Labview full system cost,
and software would be considerably more complex as NI canned apps are typically
very limited in functionality, and it takes considerable hair-pulling to
delve into their buggy libraries to get it to finally do what you want.
> > I have an ICS Electronics GPIB card and I'm using the Quick Basic
> > libraries that came with it to code a program that captures a section
> > of the displayed trace. The scope is a Tectronix TDS-210.
> >
> > The first version of the program used the RS-232 port and I was
> > capturing 512 samples of the captured trace (out of a possible 2500
> > points). I am capturing thousands of traces in a sequential manner.
> > The throughput using the RS232 port was about 1 capture per second.
> > With the new code for the GPIB port, I can capture about 3 traces per
> > second. I was expecting a MUCH higher capture rate given that GPIB
> > has a stated transfer rate of at least 200k bytes per second.
> >
> > So, my question is this: Is it typical that certain GPIB cards or
> > hardware has effective transfer rates that are much below GPIB spec,
> > or is this a case where the command or instruction-processing within
> > the device (TDS-210 in this case) is incredibly slow?
>
>
> Hi GPIB Guy,
>
> Sometimes the instrument is the limiting factor, other times your
> computer/GPIB card are the limiting factors. With some GPIB controllable
> instruments, you can output all of the trace data (one or more axes) as one
> stream, with a specific character separating the individual data points in
> the stream (e.g. all 512 data points are output at once, with a comma
> between the data for each point). With some other instruments, you have to
> explicitly ask the instrument for each data point coordinate (e.g.
> amplitude/time) individually (e.g. point 1, point 2, point 3......point
> 512). Asking for each data point individually can sometimes decrease the
> data transfer rate. Also, the format by which you read the data from the
> instrument (string, real, scientific, etc.) can affect the transfer rate.
>
> Do you know if the Quick Basic libraries are reading the data in either of
> the ways I've described above? Do you have access to the source code? (I've
> worked with Basic, but not with Quick Basic).
>
> Also, have you investigated whether a Tektronix data acquisition program
> will work for you? Test equipment manufacturers sometimes write easy to
> use data acquisition software and make it available with/for the
> instruments. I just found something about Tek's WaveStar software here:
>
> http://www.tek.com/site/ps/0,,60-12123-INTRO_EN,00.html
>
> I hope that helps...good luck to you,
> Sean