How can I limit the frequency of an external scan clock depending the number of channels?

[Jarr]

Hello friends!
I have a Daqpad 6070E and I am trying to implement one VI which limit the number of channels I am acquiring or the frecuency of the external scan clock according to the specifications of this card.  For example, I think I can't sample 16 channels with a frecuency of 1.25 Mhz of the external scan clock. Is it true? What must I have to take into account.?
Thank you.

Mensaje editado por Jarr

[Cristobal]

Hello,

yes, you are right. If you multiply the number of channels to acquire by the sampling rate, this must not go beyond 1,25 MS/s.

Moreover, depending on the API you are using to program your application ( traditional ni-daq or daqmx ), you will get errors or warnings. Doing a test in LabVIEW, I have got error -10694 using traditional ni-daq and -200019 and 200012 using daqmx.

I hope this helps.

crisR

[Jarr]

Hello CrisR.  Thanks for repply!
I am using the Acquire N Scans - ExtScanClk.vi (ni-daq). With a function generator I am simulating a TTL as external clock.  When I sample 5 channels and I increase the frequency of the TTL about 125 Khz, the vi stops, but there is no error, only the timeout.  Do you know why this phenomenon? Can I know this frequency restriction looking the DAQ manual?
Thanks in Advance

[Cristobal]

Hello Jarr,

I don't know exactly why is happening that phenomena but which is the value of number of scans to acquire?

What happens if you try with lower values?

Regards

crisR

[Cristobal]

Moreover,

what happens if you increase the time limit to 10 seconds or more?

crisR

[Jarr]

Hello CrisR! Thanks!
I have solved my problem increasing the pulse width of my TTL signal.  Now, I can increase the frequency up to 1 Mhz.  My question is if the maximun frequency of the external clock I can apply for a good acquisition is the same as the internal clock (Max sample rate/number of channels).
Thank you in advance.

[Cristobal]

Hello,

yes, I think so. The maximum external clock must not exceed the maximum sampling rate of the board. If not, the data will not be correctly acquired.

Regards

crisR

[Jarr]

Thanks for your advices, CrisR!!!
Best Regards.

Mensaje editado por Jarr