Timeline for Piezoelectric showing strange, slowly fluctuating periodic background noise
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| Nov 1, 2019 at 15:19 | history | edited | SamGibson♦ | CC BY-SA 4.0 |
Removed signature per site rules: https://electronics.stackexchange.com/help/behavior
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| Oct 31, 2019 at 13:03 | vote | accept | Kouichi C. Nakamura | ||
| Oct 30, 2019 at 21:35 | comment | added | Kouichi C. Nakamura | Thank you, guys. Mains hum noise is at 50 Hz and the sampling rate is 100 Hz. I thought aliasing is most prone to happen when the sampling rate is lower than the signal, but maybe not necessarily? In our case, Nyquist frequency is 100/2 = 50 Hz, so it's just at the borderline to get aliasing noise?. | |
| Oct 30, 2019 at 14:56 | comment | added | Peter Smith | I concur with @BrianDrummond; if you were to lock your sample rate to the mains frequency (so it is truly double the mains frequency) it would be (mostly) eliminated. | |
| Oct 30, 2019 at 14:27 | comment | added | Scott Seidman | How are you amplifying the piezoelectric element? | |
| Oct 30, 2019 at 14:17 | history | edited | Kouichi C. Nakamura | CC BY-SA 4.0 |
added 95 characters in body
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| Oct 30, 2019 at 11:42 | history | edited | Kouichi C. Nakamura | CC BY-SA 4.0 |
piggyback?
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| Oct 29, 2019 at 22:33 | comment | added | user16324 | Mains hum aliasing with your sample rate. | |
| Oct 29, 2019 at 20:33 | comment | added | Cristobol Polychronopolis | I'd first look for the obvious, acoustic signals which may be coupling into the containment structure. It looks like around 250-400Hz, quite likely resonating with a similar vibration or with a part of the structure to produce the beat pattern shown above. I don't think the gain is changing, it's more that the peaks of the signal are piggybacking on the noise. This leads me to suspect your scope speed is too low for the noise source and you might be aliasing higher frequency signals down with your slow scope sampling speed. | |
| Oct 29, 2019 at 19:04 | answer | added | Spehro 'speff' Pefhany | timeline score: 6 | |
| Oct 29, 2019 at 18:57 | history | asked | Kouichi C. Nakamura | CC BY-SA 4.0 |