Re : DAQmx: read recent sample while logging to tdms file

[kokoloris]

Hi!

I want to use the DAQmx logging function to write my measurement data to a tdms file. The measurements are taken at a high sampling frequency (50kHz to 10MHz). Meanwhile I need a few samples in my automatisation software for controlling purpose. Therefore a sampling rate of 10Hz is totally sufficient.

Until now I dindn't manage to configure the tdms logging and only read one sample per channel by usind DAQmx Read every 100ms. Also the DAQmx Read setting "RelativeTo: MostRecentSample" seems not to be available while logging data.

Does anyone have another approach to read one sample per 100ms while logging data?

Best Regards,

Dennis

[TamMou]

Hi Kokoloris,

You can use the TDMS Write function after you acquired the data with DAQmx functions as shown in the attached example.

But note that this is a software-timed example and if you want to be more precise you can turn it into a hardware-timed VI by wiring a source to the DAQmx Timing VI.

[kokoloris]

I am using a realtime system and I want to take advantage of the direct logging of data from the card's buffer to the harddisc:

http://zone.ni.com/reference/en-XX/help/370466V-01/mxcncpts/datalogging/

Therefore I don't want to use DAQmx read to acquire all samples, because I'm afraid it is too much data...

[TamMou]

Ok, in this case, the best solution would be as shown in the example "Voltage Continuous Input.vi" that you can find under 

Help>Find Examples>Hardware Input and Output>DAQmx>Analog Input 

or like in the attached example if you want to split data between several files.