PCI-6052E doesn't save all data, buffer too small?

[may lee]

WinXP,Labview6.1,PCI-6052 board,collect data from all 16 channels every 5 seconds

(Test 1)
I set external scan clock 10KHz, external channel clock 200KHz, buffersize 10K, "number of scan to read" 10K, theorically, in each file I should have 50,000x16 data. But my result is not right: every 5 seconds I got a file, but in side those files, the data is either 3000x16 or 2000 x16 alternatively. For example:
File1 is 3000x16
File2 is 2000x16
File3 is 3000x16
File4 is 2000x16
File5 is 3000x16
File6 is 2000x16

During the simulation, I see some change in the "scan backlog", but the number is not accumulated, for example, the numbers appeared are,36,0,0,..89,0. No error during the simulation. But when I stop the program I got the error: AI read is not enough fast for the data acquisition...

(Test 2)
When I set external scan clock 5KHz, external channel clock 100KHz, buffersize 5K, "number of scan to read" 5K, my result is right: I got a file every 5 second, and in each file therea are 25,000x16.

Why some data missing in the test one? The PCI6052 board clock is 333KHZ, so my setting of external scan clock and channel clock should be ok. The number of scan to read is set to as the scan rate, so I got accurately one second tiem. Is there something related with the board buffer size and setting or computer is not faster enough?

Thanks very much for help

[JenK]

There are a couple different possibilities for why the data is not all in one folder in Test 1. First of all, I noticed that you expected each file to have 50,000x16 data, but you said that each file had 3000x16 and 2000x16. Is that correct or is it 30,000x16 and 20,000x16? If what you initially said is correct it looks like you might be losing some data. However, if you meant to say 30,000x16 and 20,000x16 it looks like all of the data is there but it is just in separate files.

You are trying to read a lot of data in a little bit of time, so it is very possible that your computer cannot keep up with your settings. Also, the type of file you are trying to write the data too could be the reason you are not seeing all of your data. Excel is very slow and if you are writing to an Excel spreadsheet this could also be the reason.

The numbers that you were seeing in the "scan backlog" look fine to me. When the number increases that means that you have data in the buffer that is ready to be read. When the number drops to zero that means all the data has been read. So, what you are seeing is not a problem.

Do you have to read at such a fast rate? If not I would just keep it like test 2.

Hope this helps.

Jenk