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NI 9222 Data Loss?

Disclaimer: This is not my data, I'm just reviewing it! I have very limited information on the actual nature of the hardware. I have absolutely no access to the original setup or hardware. 

 

I've got two data recording devices that are both set to a sample rate of 200,000Hz recording data from the exact same sensor.

 

Device 1 uses a 9222 module in a cRIO chasis

Device 2 is a Dewesoft Sirius ACCv2

 

Although they are both recording at 200,000 Hz, there is a linearly increasing offset between the two. (see slide 1)

 

In slide 1, the 9222 module (blue) is a voltage reading module from NI and the orange is the Dewesoft. Based on the slide, I believe these are connected to the output of the exact same instrument.  I have both the data files and I know that the leading edge of the data was manually matched up to compare results. The author thought both devices were acquiring data at the same rate (200 kHz) and came to the conclusion (incorrectly) that the data doesn’t match because of “phase lag.” In fact, it appears that the Dewesoft is recording at more like 252,000 Hz (see slide 2)  after some basic analysis (assuming the NI is "true" recording rate. I’m very familiar with the NI 9222 modules and I’ve used them for years, the LabVIEW software automatically adds the x-step width to the header of the output file and this indicates that the 9222 is recording at the expected 200,000 Hz. Of course, not having the actual equipment to test I can’t verify that either!

 

When I redo the Dewesoft sampling rate the curves line up exactly (Slide 3), which is expected. Is it possible that the 9222 is actually losing data points but still showing a fixed x-step width? Wouldn't it crash or throw an error?

 

Thanks!

 

Slide 1.jpg

Slide1

 

Slide2.jpg

Slide 2

Slide3.jpg

Slide 3  

 

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