Accelerometer has noise every 50 Hz

[El_salinho]

We are conducting a shaker bench test on a satellite part and after checking the spectrogram we have noticed a noise every 50 Hz on several accelerometers.

Our grid is 50 Hz so we assume it may be something related to that, what is confusing is that it repeats at 100, 150, 200 etc.
It also became more noticeable later in the testing, after we have done already 2 axis.
We went back to check older data and the same issue appears but a lot more faint.
It also does not show in the FRF or PSD graphs, only in the spectrograms.
Does anyone know what else could be the reason, if the grid has really something to do with this and how/if we can filter those out?

 

[GregLocock]

You have ground loops. Switch to battery power for your measurement gear and make sure you have one main grounding points. Good quality charge amps have the option of grounding the signal to the casing, I used to regularly have to change that over the course of weeks.

The harmonics come from power supplies etc, and are normal. Is there someone more experienced you can talk to?

Cheers

Greg Locock


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