how to achieve high sample rate using two DMM 4065 simultaneously or just one ?

[AndrewZhu]

Hello all, 

     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.

Andrew

[crossrulz]

Duplicate thread

[Blizzard]

Hi Andrew,

In order to increase the sample rate, you have to decrease the resolution of your DMMs. I would try using the shipping example in the NI Example Finder under Hardware Input and Output>>Modular Instruments>> Switch> NI-DMM>> Multi-Point Measurements>>  Cont acq & Chart Multiple Samples.vi. Using this VI, decrease the resolution to 4 and 1/2 digits. See if you can achieve a higher sample rate using this method.

Also, you can save  your data in a variety of ways. You can use the Write to Measurement File Express VI to save your data to the file type of your choice. Additionally, you can use the Write to Spreadsheet file with Active X controls to save to an Excel file. 

I hope this helps!

Anna L

[AndrewZhu]

Hi Anna,

   Thank you. Your suggestion is absolutely right.  The problem has been solved independently by two ways: using Cont acq & Chart Multiple Samples.vi  and Maxmizing DC reading. vi. 

Andrew