03-20-2014 08:38 PM
I have been working on collecting data using two DMM 4065 (for current and voltage) which I recently purchased from NI. These two DMMs along with a few other modules (including a switch) were pre-installed to a PXI-1036 system. I followed the examples and tried my best but still could not get a high sample rate using my VIs. The max sample rate I can achieve now is about 25 samples/s. However, it seemed the DMM itself was sampling at around 3000/s using the included " Maximizing DC reading vi" example, and this could also be seen when using a waveform chart. However, the waveform chart does not show correct time and have limited default data storage, so I created a XY graph which showed the current time but it lowered the sample rate significantly. What I need is to achieve high sample rate simultaneously for the two DMM 4065 , and if two is not possible, one should also work as long as it has high sample rate (>200 samples/s) . I have attached two VIs I modified from the examples. Any help is greatly appreciated.
P.S. I ran the sample vi " Maximizing DC reading" with only added a waveform chart, the total points acquired were 17702 at a rate of 2974, as seen in the attached figure. I then exported the data from the wave chart, it only showed 104 data points. I am confused why the two showed different data points when they were sharing the same data source. And is there any way to export the acquired 17702 points to a txt or excel file? Thanks a lot.
03-21-2014 05:09 PM
Try writing your data to a file rather than pulling it off the chart. That should give you every data point the DMM is reporting. You could use a write to measurement file express VI for starters and then move to lower level VIs.
There is a good white paper discussing TDMS logging here
03-21-2014 05:41 PM
Thank you. Your suggestion is absolutely right. It has been solvd by this way.