Wow and Flutter measurements like you've never seen before! Maybe...

[lsorrentino]

can the rpm data from the measuring device be exported to Excel ?

Logarithmic x axis makes it easier and more relevant to read

I can upload the data, they are csv and can be imported in many sw.
Nope, in this case log x axis is not much of help, but when I sit in front of the pc I will upload log plots for yuor information.
For example to automatically find peaks, it was better to use a linear y axis too.

 

[Sleiven]

I Get this from Shaknspin when I import to my Excel sheet, The FFT is done in excel and clearly shows the 0.55 and 1.1 peaks log scale 0.1 to 100hz. The DIN and WRMS weighting hides many faults and can be quite misleading, the plots tell me much more,



Here is my Denon 51F first on test record , then on Shaknspin/Excel


main disturbance is flutter at 5hz, The orange plot is relative values to the highest peak =1. The once per revolution 0.55Hz eccentricity from the test record is gone…

 

[lsorrentino]

Very interesting. I was tempted to buy shakenspin too.
My aquisition is 300,000 samples 1k sample per second.
Making the FFT direct on all the samples at the same time permits me to have a freq resolution of 3.3mHz starting from 0 to 500Hz .
If you look at my uploaded graph you can perfectly detect all the harmonics starting from 0Hz that represents dc value -> constant velocity that I've nomalized to 0dB, 3.49 rad/sec for my sensor, ending @ 500Hz.
I have not made a plot with speed variation like that, but I've caculate a polar plot that represents the same infomation based on the average of 50 turns.

 

[Mark 1234]

Interesting... I just tried a phone app not playing a record (needle up) and playing one (needle down)
Pretty close. Never tried that before.

 

[lsorrentino]

Logarithmic x axis makes it easier and more relevant to read

Here you have the log plots. dB values refers to nominal 33+1/3 speed and are RMS, for direct W&F calculation.

 

[lsorrentino]

I just tried a phone app

Yes some are very good, I use this one "RPM speed and WOW", for speed variation is very good, not for the absolute value in my case. Hi freq flutter is not measurable, as far as I know.

 

[JP]

Hi, Balle.

My data weren't FM demodulated, just the FFT of gyroscope data of the Z axis of my sensor.
I'm still thinking that I can not understand exactly how can you determine this plots are from not working units.

I understand what the plots are - I’m suggesting things that are more useful to examine.

I’ve already said why I think the ‘tables may not be operating correctly. You can’t verify proper operation just from a W&F number - that’s like trying to verify an amplifier is operating per design based solely on THD.

 

[fasterbyelan]

I've just seen this thread.

I'm a big Lenco fan and did carry out similar work a few years ago using some software I was given (see here). The most probable reason for the elliptical shape is that the platter is not flat. I replaced mine with a flatter one, which improved things but as I was using a record to generate the test tone, I always had the record-centering issue to contend with.

I now use a Turntable Speed app to check that things are OK. This is the result after the TT has been serviced.



Karl

 

[mr_petit]

Yes some are very good, I use this one "RPM speed and WOW", for speed variation is very good, not for the absolute value in my case.

Phone apps and phones themselves are notoriously bad at this.
a very simple test that most people seem to forget to do but should be done with any test equipment:

 

[cafe latte]

Sorry for the poor quality image. This is my friend's Commonwealth idler drive. Beats SP10MK2
Chris

 

[cafe latte]

Phone apps and phones themselves are notoriously bad at this.
a very simple test that most people seem to forget to do but should be done with any test equipment:

Yep phone apps are pointless.
I have measured high wow and flutter with my phone and much lower with a shaknspin. Phones are not calibrated and they are heavy, even trying really hard they mess with balance. A Shaknspin is another story.
Chris