Acquiring analog signals from multiple channels using NI 6251

[jerryjog]

Hello Everyone,

I'm using NI 6251 DAQ to acquire analog signals from multiple channels (actually 3 channels). I set the sampling rate to 1MHz and the Number of samples to 70000 for each channel. It seems that the DAQ card is unable to perform the data acquisition properly, erros include "some or all of the samples requested have not yet been acquired". According to the mannual, the DAQ card does support 1MHz sampling rate for multiple channels, is it because the number of samples is too big (but I really need that large amount of samples)? Can anyone give me some advice? Thanks in advance!

Best

Jerry


Message Edited by jerryjog on 04-06-2008 11:52 AM

[Matt_A]

Hello Jerry,

As described in the NI 625x Specifications, the NI 6251 supports an aggregate sample rate of 1 MS/sec. Please see the below excerpt from the specifications:

A maximum aggregate sample rate of 1 MS/sec means that you must divide that rate by the total number of channels to determine the maximum sample rate for multi-channel acquisition. This topic is discussed in more detail in the section called "Sample Rate Considerations" in the NI-DAQmx Help. You can find this document by navigating to Start>>All Programs>>National Instruments>>NI-DAQ. I have copied this section below for your reference.

So, if you reduce your acquisition rate to 333 kS/sec you should be able to acquire all 70,000 points without a problem.


Message Edited by Matt A on 04-07-2008 10:41 AM