sample rate problems

[Matt G]

There is a somewhat generic problem I've been experiencing using LabView with GPIB instruments.  Signals are generated at either 5 or 90 hertz, but the computer can only acquire <5% of generated signals, frequently not that well (esp for higher freq).  Is this a GPIB problem, poor programming (this would have to be acrosss multiple instruments), or a LabView problem?
I can attach VIs if anyone might have some insight, but this is for all VIs I've used.  Any help in this regard would be greatly appreciated.

[Dennis_Knutson]

I would suspect either a programming problem, instrument limitation, or GPIB limitation (in that order).

You should attach your code and also provide details on the make and model of instrument.

[Matt G]

The first attached file is one of the programs that runs much slower than expected.  The second file is the VI tree for the subVIs used in this particular program.  While stripping out the graph updates speeds it up a little, I'm still not sure what causes it to take too long.  Cutting down the timeout parameter has helped, but that might be through omitting runs.

[Matt G]

The instruments used in these programs are a tektronix 220 (GPIB controlled via USB-GPIB converter) and a Horiba Jobin Yvon iHR320 monochrometer (USB controlled). 
Thank you for your help.

[Dennis_Knutson]

Looking back at your original question and the VI, I think I might have misunderstood your problem. Is your problem that you are not getting a continuous signal? Is that what you mean by <5%? If that's the case, then that is a basic limitation with the instrument and GPIB. Most scopes will need to be triggered, then acquire, then do a transfer. It will require x amount of time to do these. It is usually a sequential operation so while the instrument is performing the data transfer to the pc, it is not acquiring. Only when the trasfer is complete will it rearm and acquire.

[Matt G]

I'm not certain how long the oscilloscope (Tek 220) takes to upload data, but its screen refresh rate is visibly and significantly faster than data is uploaded to the computer.

[Dennis_Knutson]

Yes, that's normal. If you want a much faster transfer rate, a scope card in the pc is going to be much better (10x at least).

[Matt G]

Thanks for resolving that.  Hard to tell where limitations come from sometimes.