Analog input and low frequency "synchronisation"

[j0rdi]

Hello I am using LabVIEW 7.1, and my chassis consists of a NI PXI-1031 with one DSA PXI-4472 and two NI PXI-6221. I am acquiring analog data from all cards. All cards are synchronizes using the master as PXI-4472. I am working in continuous samples mode and am using different rates like 100 Hz or 1000 Hz.  I am trying to measure and log low frequency with PXI-6221 using a Method 1 (Measure Low Frequency with One Counter).  I don’t have any problem to acquiring frequency, but as the frequency measurement uses an implicit timing how can I add frequency in the same file than the analog inputs using the analog time sampling rate? (Data is being transfered to the file in parallel with the acquisition.) Thanks.

[sendia]

Hi Jordi,

There is no way using driver NI-DAQmx to set programmatically an acquisition rate in a frequency measurement task. This kind of tasks has an implicit timing and it cannot be changed. The only way you can write a frequency value for each signal measurement, is rewrite the frequency value as many times as signal points you acquire. For example, you can put the signal acquisition, frequency measurement and the data logger in the same loop and repeat the value of frequency measurement (see attached file).

Regards,