speed of signal collection

[opal]

Hi,

I'm trying to collect signal from my old Tektronix diginal signal analyzer (DSA602A) by GPIB. I downloaded the labview driver (dkdsa600.dll) from NI.com and simply connect the GPIB pci card to the DSA602A by GPIB cable. Finally, I got the signal collecting going on quite well. However, each scan will take about 2sec. By looking into the "Tek DSA 600 Read Wfm.vi", I found the most of the time was consumed by the function "GPIB read" with 32768 in byte count.

So, my question is is it normal to spend 2 sec to read 32768 numbers through GPIB? If not, what part, such as  scope and computer will casue this time delay. Thanks.

Opal  

[LabVIEW_Joel]

HI Opal,

2 sec is a reasonable amount of time.  I once had a 14 sec delay using an arb and transfering a waveform of 55K points.

You might be able to speed up the tranmission if you have the inst use binary instead of ASCII.  The ASCII chars can have a variable width, where the binary numbers will have a fixed width.  Check the manual to see if you have control over the transfered data's format (some inst don't expose this option).

As long as you are not losing data, then you should be OK.  If there are less than the 32768 bytes, the inst will return sooner.

Let me know if you have any problems.

Joel

[GPIB_Guru]

The throughput that you are seeing is about 16kB/s. The maximum rate of IEEE 488.1 3-wire handshake is about 1500kB/s. A more typical rate would be about 300kB/s, which is still significantly larger than you are seeing. My guess is that by the time you are starting your read, the device has not finished collecting/calculating the data. Moving to binary should make the device have less processing to do, which could increase your throughput. However, since this is an old instrument, it may be using older GPIB technology that sends data bytes one byte at a time instead of streaming using FIFOs. You should check the user manual to see what the maximum throughput the instrument is capable of.

[opal]

I can't find the manual for DSA602A, but I do find some information about that instrument in Tektronix website.

it said that:

"Data Transfer Rates: Up to 100 waveforms per second. Up to 60 measurements per second".

The rate is much smaller than rate of moden oscilloscopes which have at least 3000 waveforms per second.

Does that means my oscilloscope is slow?

Thanks