Delay in Acquiring Signal (M series +SCXI modules)

[phanisrikanth]

Hi,

My RT Data Acquisition System setup consist: PXI-8106 with three PXI-6254 modules(M-series), SCXI-1001 with four SCXI-1125 modules Max Sampling Rate:10K when I configure all the channels (count:64, both PXI and SCXI channels) and acquiring, I am observing a seven seconds delay of signal updating. For example: 5V signal is applied, in software I can see that only after 7secs. Read Pallet in RT code itself showing 7 SEC's old data. Note;For individual channel and few channels s/w updating has no problem. As other DAS's are acquiring(updating) fine for the same signal. ->will this problem occurs with SCXI modules.

Please clarify my doubt

Thank you for any help in advance,

regards srikanth.

[sumit.sen]

How are you observing the data? Are you using Interactive Front Panel Communication or running a separate host UI vi taking help of network-published shared variables?

[Exp_Design]

Hi,

Could you tell us more about the physical setup and your programming?

If you have a host computer, you are not seeing the data in real-time due to TCP/IP.  If you are attempting to see all 64 channels on your monitor, it will take a bit for the host computer to crunch through all that and update accordingly.  Recording data will also cause the host to slow down especially at high sample rates.

You can check by sending an event signal on any spare analog channel to indicate the start of an acqusition and the end of the acquisition.  During the acquisition stimulate a channel with a known voltage 10 seconds and 30 seconds after the start event.  The data on the screen should show you the system is accurately recording data WRT to time.

I would also suggest you record the data if you are not already doing so with a time stamp to again analyze your data to see if there is a problem.

James