Can I using external trigger signal to trigger the acquisition of PXI 5105, and fetch the data simultaneously

[g_l_g_s]

Dear all,

I 'm using a PXI 5105 to acquisite data from channels, it need to be triggered by a 25Hz external signal. Firstly I using a sequential method, i.e. acquisition + fetching. By using performance analysis, I found the average data fetching time is 52 ms. So in my current program, data acquisition is 40ms, and then data fetching 52 ms, during this time, 2 new triggering signal are omitted, and this make the period of one DAQ is about 120ms, too long for my application.

I want to know is there method that the triggered data acquisition and data fetching can work simultaneously, then I can reduce the period to about 50ms or so.  I try to separate the data acquisition and fetch into 2 independent while loops, but found that the data acquisition are working all time but data fetching never work. Could you give me some clues to solve my problem, thank you! 

The graph of my current program is :

  

[Henrik_Volkers]

Have a look at the example niScope EX Multi Record Fetch more than Available Memory.vi

LabVIEW Description:

This VI demonstrates the multi-record and continuous acquisition capabilities of National Instruments digitizers.  In a multi-record acquisition, each record is one waveform with at least "min record length" points as specified with the Configure Horizontal Timing VI.   Furthermore, each record is triggered, so when the trigger arrives for the first record, the hardware quickly rearms for the next record.  Refer the to Multi Record example for more information.

In this example, the Fetch VI is used with the Fetch Record Number and Fetch Number of Records properties to fetch each record individually.  Using the Fetch VI with a positive timeout only waits for the requested waveform to be done - rather than waiting for all the records.  In this example, the fetch VI only waits for the next record, and then it retrieves the record while it is acquiring other records.

The Allow More Records Than Memory property is a Boolean value that allows you to configure more records than fit in the onboard memory at one time.  When this is enabled, you can specify any number of records.  The records are treated circularly in the onboard memory, so you must fetch them before they are overwritten.  If you attempt to fetch a record that has been overwritten in the digitizer's memory, an error is returned.  

[g_l_g_s]

Dear Henrik, Thank you for your clue, I will try to use the method mentioned in the example. Guangjun