from E series to M series screen value update question (very simple)

[zmarcoz]

Dear all,

 I help my friend to update the LabVIEW code from traditional DAQ to DAQmx becuase he changed his device from E to M series. He found out that numical values in the front panel updated faster after updated. I told him that the new device has a much faster sampling rate, so it makes sense for the numical values and graph update faster. However, someone in a forum told me that "The sampling rate is setup by the labview application and should be the same for both DAQs (126kHz)."  I am not sure where that guy from the forum find out the number, but I have no clue whether my answer or the forum guy's answer is correct. Please help

http://sine.ni.com/nips/cds/view/p/lang/en/nid/202597

http://sine.ni.com/nips/cds/view/p/lang/en/nid/2601 

[Hillman]

Hi Zmarcoz,

Thanks for your post and I hope your well today.

From looking at the specifications for the devices on ni.com there following information can be found, 

USB 6251 ( M Series) has an Analog Input Sample Rate of 1.25 MS/s

PCI 6052E (E Series) has an Analog Input Sampel Rate of  333 kS/s. 

Therefore you are correct that the M Series can acquire more samples per second than the E Series device. 

However the DAQmx API in LabVIEW allows you to set the sample rate. Using one of the e xamples you can see the Sample Clock has a rate input. If you set this to 1000 (1kHz) you will get a sample 1000 samples every second ( a sample every 1ms). Now if your performing a continous acquisition you should aim to read 10% of the buffer per iteration of the DAQmx Read.vi - so you would set the Number Of samples to 100. Thus your loop must iteration every 10ms to prevent loss of data (and error). i.e. 10 (reads per second)  x 100 (Number of Samples) = 1000 Samples per Second (Hz). 

I am currently unsure of the 126kHz - was this the sample rate you were using before? Because the DAQmx code could be setup to have the same rate!

I hope this helps,