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25th Nov 2020, 03:42 PM #16Member: Blue and white apron brigade
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 7,182
There are indeed heaps of Apps some that a better than others..
For slower speeds there are apps that use the phones inbuilt accelerometer, some of which claim to measure up to 50Hz (3000rpm) so measuring 33rpm is a doddle.
In practice reliable measurement these accelerometers are only good up to about 25Hz (1500 rpm)
I use a App called Vibration to measure - vibration - what else. It's accelerometer readout stops at 25Hz.
It also depends on how clean the vibrations are, as usually you have to pick the main vibration peak out amongst a whole lot of other noise peaks.
If its a smooth rotation like a turn table then the it's quite easy easy, but if not, the numbers can be all over the place.
To measure above 25Hz you need an app that uses the inbuilt microphone but between 25 and 50z the responses of most phone mics is ordinary so don't expect that reliable a result.
The phones don't need to be strapped to rotating shafts etc to detect the vibe.
Usually enough vibe can be picked up by placing the phone on a surface in direct contact with the vibe source eg motor.
Adding a small off axis weight to accentuate the vibe can help.
Here I'm using the Vibration App on an iPad to measure the vibrations of a dust extractor impeller under that 6mm steel plate.
Ipad.jpg
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2nd Dec 2020, 07:27 PM #17Member
- Join Date
- May 2018
- Location
- Cairns, Qld.
- Posts
- 70
Rpm indication
Well, I received the previously ordered fleabay hand-held laser strobe rpm indicator a day or two ago (About $25 delivered), so proceeded to check it vs the hall-effect rpm indicator system that initially prompted this query. Short answer; both indications agree within 1 or 2 rpm up to about 2900 rpm which is the highest reading I can find on my workshop machines (Bench Grinder). Lowest was less than 100 rpm on a lathe chuck. So all is fine.
As suspected, the posted rpm table on my HF-46 mill (for 50hz operation) shows about 6% low at each of six speed selections. Not a really significant issue, but now we know. Correction chart to be filed away somewhere.
Another gadget for the tool collection.
Thanks for all the responses.
Halifax 614
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2nd Dec 2020, 07:45 PM #18
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2nd Dec 2020, 08:37 PM #19Member: Blue and white apron brigade
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 7,182
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