I'm using the RP (stemLAB 125-10) as a DAQ system for acquiring data from pipe leak using an ultrasonic transducer. The RP is controlled via SCPI using a python script running on a laptop, ultimately the goal is to measure the RMS of a fixed number of samples. Right now the script acquires a buffer worth of data points at a decimation of 64 without a threshold.
I'm getting all sorts of strange behaviour in the acquired signals and I have absolutely no idea what is causing it. It's probably easiest for me to show you what I mean:
Exhibit A:
Exhibit B :
Exhibit C:
Exhibit D:
D shows what would be an 'expected' recording, I believe this was recorded using a pre amplifier. However, even with the pre amplifier more often than not the recordings would contain the strange behaviour seen in the other recordings. Notice in B at 8e-3 seconds the signal changes completely and shows what I would have expected to measure, it's much more similar to D.
Note: C was recorded without the leak running.
My first thought was that it was a grounding issue but from my research I couldn't see how to properly ground a RP. I'm not sure if its clear from the photos but the calibration is out of whack, I was planning on just applying an offset to the acquired signal rather than going through the rigamarole of doing it properly (I'm unfamiliar with the process and the calibration equipment).
I understand that the stemLAB 125-10 is a much older model so I plan on re-running the tests with a 125-14. I should mention I tested two different 125-10's to see if one of them was broken but got similar results on both, they were both shoved away in a cupboard so it may well be that they were both broken.
If anyone has any advice that would be really appreciated because I'm completely out of ideas now.
I'm a beginner at this sort of stuff so hopefully someone with a bit more experience could give me some support. Please let me know if there's any further information I can provide.
Cheers,
Jamie.
