s series 100k or 2M

[barak]

Hi,

I'm using 6133 card, Labview 8.2 and daqmx 8.3

I use the example for using counter0 as pulse train retriger to sample continusly signal.

The problem is that not for all scan rates i use i get a correct respond.

I read in the documantation that the freq of the timer is 100Khz or 20Mhz,What thats meen?

Can i use ant scan rate as i want (10Khz,20Khz,30Khz......).for 10Khz i get good result( the accurate number of samples i want) but for 30Khz for example i get strange results.

I assume that there is some kind of divider in the card that divide the base freq(100Khz/20Mhz), but i didn't found anything

in the documentation.

please help!

[Paul_C.]

Hi Barak,

The 6133's counters have a maximum allowable frequency of 20MHz with a minimum pulse width of 10ns high or low.  On pulse train generation, the counter source signals is typically generated using either the onboard 20MHz or 100KHz timebase.  I'm assuming that you are using the counter output as the sample clock to sample continuously.  You should be able to specify any rate that is a integer divide down of the internal timebase.  Could you explain what "strange results" mean with the 30KHz scan rate.  I assume you are using the counter output as the sample clock for an analog input.  Is this correct?  If this is the case, the specified rate of the counter would determine your sample rate.  When doing continuous sampling, the number of samples will be determined by the amount of time and the sampling rate.  I would recommend taking a look at the article found here.  It has some really good information on how the sampling rate is determined.

I hope this helps,
Paul C.

[barak]

Hi Paul ,

Thanks for your answer.

Ypur assmaption is right.

The strange behaiur is that :

After doing some more resarch i found out that it happens in all freq and not only 30khz.

for one triger at a counter freq of 10Khz for example,  get this results:

when samples to read = 10  ==> number of sample available property = 0.

when samples to read = 16  ==> number of sample available property = 16.

when samples to read = 20  ==> number of sample available property = 16.

It looks like the tranfer agorithm from the card to the RAM by the DMA is working in chunks of 16 bytes only.

I heard from one of the ennginers in israel that he knows about a problem like that in the e- serias card.

My card is s series.

Any expalnation to that results?

Thanks for your help.