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I am working on my own little project where I need to do detect CNC machine spindle vibrations. The spindle spinning up to 30000rpm and vibrations expected are less than 1mm. I have purchased lis3dh module and tried to run some Arduino program on it. It seems that the sensor output is very noise. When the sensor is standing still on my table, the readings are as following:

08:43:18.224 -> X: 491 08:43:18.224 -> Y:-15883 08:43:18.224 -> Z:-1230 08:43:18.224 -> X: 518 08:43:18.224 -> Y:-15862 08:43:18.224 -> Z:-1529 08:43:18.224 -> X: 302 08:43:18.224 -> Y:-15915 08:43:18.224 -> Z:-1260 08:43:18.224 -> X: 472 08:43:18.224 -> Y:-15948 08:43:18.224 -> Z:-1350 08:43:18.224 -> X: 435 08:43:18.224 -> Y:-15892 08:43:18.224 -> Z:-1243 08:43:18.224 -> X: 595 08:43:18.224 -> Y:-15840 08:43:18.224 -> Z:-1398 08:43:18.224 -> X: 406 08:43:18.224 -> Y:-15867 08:43:18.224 -> Z:-1158 08:43:18.224 -> X: 584 08:43:18.224 -> Y:-15857 08:43:18.224 -> Z:-1537 08:43:18.224 -> X: 291 08:43:18.224 -> Y:-15924 08:43:18.224 -> Z:-1452 08:43:18.224 -> X: 428 08:43:18.224 -> Y:-16041 08:43:18.224 -> Z:-1419 08:43:18.224 -> X: 446 08:43:18.224 -> Y:-15883 08:43:18.224 -> Z:-1569 08:43:18.224 -> X: 596 08:43:18.224 -> Y:-15905 08:43:18.224 -> Z:-1304 08:43:18.224 -> X: 430 08:43:18.224 -> Y:-15865 08:43:18.224 -> Z:-1372 08:43:18.224 -> X: 489 08:43:18.224 -> Y:-15796 08:43:18.224 -> Z:-1051 08:43:18.224 -> X: 612 08:43:18.224 -> Y:-15865 08:43:18.224 -> Z:-1232 08:43:18.271 -> X: 510 08:43:18.271 -> Y:-15832 08:43:18.271 -> Z:-1308 08:43:18.271 -> X: 502 08:43:18.271 -> Y:-15916 08:43:18.271 -> Z:-1436 08:43:18.271 -> X: 251 08:43:18.271 -> Y:-15939 08:43:18.271 -> Z:-1284 08:43:18.271 -> X: 462 08:43:18.271 -> Y:-15891 08:43:18.271 -> Z:-1667 08:43:18.271 -> X: 417 08:43:18.271 -> Y:-15830 08:43:18.271 -> Z:-1486 08:43:18.271 -> X: 492 08:43:18.271 -> Y:-15884 08:43:18.271 -> Z:-1497 08:43:18.271 -> X: 516 08:43:18.271 -> Y:-15784 08:43:18.271 -> Z:-936 08:43:18.271 -> X: 459 08:43:18.271 -> Y:-15963 08:43:18.271 -> Z:-1497 08:43:18.271 -> X: 444 08:43:18.271 -> Y:-15809 08:43:18.271 -> Z:-1270 08:43:18.271 -> X: 291 08:43:18.271 -> Y:-15916 08:43:18.271 -> Z:-1353 08:43:18.271 -> X: 425 08:43:18.271 -> Y:-15779 08:43:18.271 -> Z:-1254 08:43:18.271 -> X: 580 08:43:18.271 -> Y:-15820 08:43:18.271 -> Z:-1097 08:43:18.271 -> X: 499 08:43:18.271 -> Y:-15856 08:43:18.271 -> Z:-1091 08:43:18.271 -> X: 688 08:43:18.271 -> Y:-15772 08:43:18.271 -> Z:-1148 08:43:18.271 -> X: 451 08:43:18.271 -> Y:-15838 08:43:18.271 -> Z:-768 08:43:18.271 -> X: 536 08:43:18.271 -> Y:-15891 08:43:18.271 -> Z:-1377 08:43:18.271 -> X: 377 08:43:18.271 -> Y:-16028 08:43:18.271 -> Z:-1494 08:43:18.271 -> X: 620 08:43:18.271 -> Y:-15868 08:43:18.271 -> Z:-1376 08:43:18.271 -> X: 624 08:43:18.271 -> Y:-15984 08:43:18.271 -> Z:-1024 08:43:18.271 -> X: 563 08:43:18.318 -> Y:-15974 08:43:18.318 -> Z:-1179 08:43:18.318 -> X: 409 08:43:18.318 -> Y:-15931 08:43:18.318 -> Z:-1304 08:43:18.318 -> X: 630 08:43:18.318 -> Y:-15920 08:43:18.318 -> Z:-1356 08:43:18.318 -> X: 345 08:43:18.318 -> Y:-15905 08:43:18.318 -> Z:-1484 08:43:18.318 -> X: 566 08:43:18.318 -> Y:-15865 08:43:18.318 -> Z:-1264 08:43:18.318 -> X: 403 08:43:18.318 -> Y:-15835 08:43:18.318 -> Z:-1438 08:43:18.318 -> X: 473 08:43:18.318 -> Y:-15955 08:43:18.318 -> Z:-1248 08:43:18.318 -> X: 468 08:43:18.318 -> Y:-15825 08:43:18.318 -> Z:-1358 08:43:18.318 -> X: 582 08:43:18.318 -> Y:-15878 08:43:18.318 -> Z:-1345 08:43:18.318 -> X: 443 08:43:18.318 -> Y:-15808 08:43:18.318 -> Z:-985 08:43:18.318 -> X: 558 08:43:18.318 -> Y:-15830 08:43:18.318 -> Z:-1401 08:43:18.318 -> X: 457 08:43:18.318 -> Y:-15873 08:43:18.318 -> Z:-1036 08:43:18.318 -> X: 416 08:43:18.318 -> Y:-15956 08:43:18.318 -> Z:-1654 08:43:18.318 -> X: 419 08:43:18.318 -> Y:-15992 08:43:18.318 -> Z:-1128 08:43:18.318 -> X: 342 08:43:18.318 -> Y:-15907 08:43:18.318 -> Z:-1507 08:43:18.318 -> X: 377 08:43:18.318 -> Y:-15862 08:43:18.318 -> Z:-1174 08:43:18.318 -> X: 600 08:43:18.318 -> Y:-15881 08:43:18.318 -> Z:-1220 08:43:18.318 -> X: 574 08:43:18.318 -> Y:-15960 08:43:18.318 -> Z:-995 08:43:18.318 -> X: 467 08:43:18.318 -> Y:-15868 08:43:18.318 -> Z:-1414 08:43:18.318 -> X: 342 08:43:18.365 -> Y:-16054 08:43:18.365 -> Z:-1670 08:43:18.365 -> X: 457 08:43:18.365 -> Y:-15928 08:43:18.365 -> Z:-1644 08:43:18.365 -> X: 500 08:43:18.365 -> Y:-15974 08:43:18.365 -> Z:-1121 08:43:18.365 -> X: 502 08:43:18.365 -> Y:-15878 08:43:18.365 -> Z:-1174 08:43:18.365 -> X: 534 08:43:18.365 -> Y:-15785 08:43:18.365 -> Z:-1160 08:43:18.365 -> X: 560 08:43:18.365 -> Y:-15875 08:43:18.365 -> Z:-1064 08:43:18.365 -> X: 465 08:43:18.365 -> Y:-15936 08:43:18.365 -> Z:-1248 08:43:18.365 -> X: 643 08:43:18.365 -> Y:-15920 08:43:18.365 -> Z:-1155 08:43:18.365 -> X: 374 08:43:18.365 -> Y:-15929 08:43:18.365 -> Z:-1380 08:43:18.365 -> X: 614 08:43:18.365 -> Y:-15904 08:43:18.365 -> Z:-1481 08:43:18.365 -> X: 430 08:43:18.365 -> Y:-15926 08:43:18.365 -> Z:-1203 08:43:18.365 -> X: 492 08:43:18.365 -> Y:-15846 08:43:18.365 -> Z:-1177 08:43:18.365 -> X: 452 08:43:18.365 -> Y:-15830 08:43:18.365 -> Z:-1308 08:43:18.365 -> X: 641 08:43:18.365 -> Y:-15881 08:43:18.365 -> Z:-1081 08:43:18.365 -> X: 456 08:43:18.365 -> Y:-15889 08:43:18.365 -> Z:-1203 08:43:18.365 -> X: 444 08:43:18.365 -> Y:-15798 08:43:18.365 -> Z:-1187 08:43:18.365 -> X: 564 08:43:18.365 -> Y:-15892 08:43:18.365 -> Z:-1507 08:43:18.365 -> X: 363 08:43:18.365 -> Y:-15857 08:43:18.365 -> Z:-1292 08:43:18.365 -> X: 467 08:43:18.365 -> Y:-15808 08:43:18.365 -> Z:-1513 08:43:18.365 -> X: 358

As you can see from above, the readings fluctuate quite a bit therefore there is no way for me to tell whether thats a vibration or just random noise detected. Could someone give me any tips on how can this be achieved? I do not need very accurate results but at least something!

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  • Why not filter for 500 Hz or a harmonic, to eliminate noise? For that matter, would direct pickup from coils placed near the shaft or other vibrating part work better than an accelerometer? Commented Aug 20, 2021 at 2:31
  • Please can you elaborate a little more. My hardware knowledge is close to nothing. Commented Aug 20, 2021 at 4:10
  • If the spindle rotates at 30,000 RPM, that's 500 revolutions per second, so likely the vibration is at that frequency, in which case an LC pass filter would emphasize that frequency, reducing signal outside it pass-band. On the other hand, if you're trying to pick up vibrations such as the bit chattering against work, you might want to block noise from the spindle rotation with a blocking filter. This is a bit too complex to explain from scratch, research L-C band pass filter. Commented Aug 20, 2021 at 16:58

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