Log from Digitizer

Question

I need to log both channels of my digitizer for 8 seconds.
I need to see how 2 waveforms (both at 350kHz) are changing overtime so sampling rate needs to be as high as possible. 
Nothing fancy needs to be done. 
No triggering. No timing. No special file type. Files don't even need to be indexed. 
Just click. Log. Save the file manually. 
What is the most simplistic way to do this?
We have a bunch of NI software (Labview, Signal Express, ect..), but nobody on the team knows how to use them...
Thank you very much!
Randy
Solved!
Go to Solution.

Answer 1

The amount of data the NI-SCOPE Soft Front Panel can save is limited by the amount of data your scope can take in a single acquisition.  This will depend upon how much memory your scope has and the native bit depth of the acquisition (e.g. a 5122 takes 16-bit data).  You can change the record length in the SFP by choosing Edit»Device Configuration and selecting the Horizontal tab.  You may get where you need to be by just doing this.
However, you can get far more data and higher data rates if you stream from the device directly to disk.  This operation will be limited by your bus and disk speeds.  Typical sustainable values are around 20MBytes/sec - 40MBytes/sec, although with RAID systems and PCIe busses, this can get into the hundreds of megabytes per second.  To do this, you need to set your scope up so you are fetching from it as you are taking data.  A simple example can be found in niScope EX Fetch Forever.vi, in the NI-SCOPE examples.  However, this does not save data, it just fetches it.  After you fetch the data, you need to save it, preferably in a different thread than the fetch code.  This is easy in LabVIEW - use another loop.  You can find an example of this in niScope EX Save to File - HWS Low Level - Single Channel Stream.vi.  It uses NI-HWS, but the calls to NI-HWS could easily be replaced with either the binary primitives or TDMS calls.  This example fetches like the first one, but uses a queue to send to data to another loop, where it is stored in a file in a parallel thread.  Note that displaying your data will slow down your maximum acquisition rate, so the example does not do this.
Good luck!  Let us know if you need more help.
This account is no longer active. Contact ShadesOfGray for current posts and information.