PXI 4071 current measurement slows down after 500 seconds.

[Austin-Downey]

I am measuring the current draw of a square wave through a material. The system starts out taking about 40 S/s as shown here,

However, after 500 seconds the current measurements slow down to about 20 S/s as can be seen here. Is this a hardware related issue (e.g. I don't have enough RAM, 2 Gb, on my PXIe-8820)?  In the code, I am waiting until the end to save the data, a 3.5 Mb file but this file size has not been an issue with other I/O setups.  

Thanks in advance,

Austin.  

[SamuRei · Accepted solution]

Hey Austin, 

A LabVIEW memory consideration could very well be the issue here. If you were, for example, controlling the sample rate with a while loop in LabVIEW and storing data points in shift registers, we would expect to see this type of behavior over time. Would you be able to post code (or a screenshot) so that we could gain a little more insight into what's going on here?

Best,

[Austin-Downey]

Its been a year, but I should reply for the sake of others. 

It was a memory problem. The embedded system we were using only had 1 Gb of ram. This was solved by slowing down the acquisition speed and taking the time stamp of every sample for post-processing.