Measuring TT Speed


In measuring my tt speed I am seeing the lines on the strobe bounce back and forth, not holding steady. This is a belt tt with a dc motor setup with a closed loop controller, and ideas on what can cause this? I am thinking the belt may be to tight, it is a new belt BTW...
jsman
Tom,
Are you saying that the numbers should be stationary? That's what I have been doing wrong, I am looking at the bars. For whatever reason I thought the lines were to be stationary....
There are a lot of variables with measuring speed and W&F. That’s not to say you shouldn’t try to measure it, but take the values with a grain of salt. As an example, I get the following for the same belt driven TT:


RPM App/World TT Database: 33.33 RPM, +0.00%, 0.07 W&F
WFGUI: 0.0199% RMS W&F
Analog Magik: 0.0443% AES W&F
I prefer and feel more confident with the off board Strobe.
They usually cost the price of a Vinyl Album or Two, and don't get a lot of usage once utilised.
A Strobe built in to a TT can offer inaccuracies in showing the Speed,
it is worth reading up on some of the descriptions how this can be happening.

  
the RPM app for cell phones is accurate and a lot easier to use than a strobe. Check it out !
In my phone LG v30+ RPM metter shows 32.83 instead of 33.33
Both my turntables has strobe's and one of the even has custom built. And if I do measure friends machines I am getting the same error always so for me it's usable but it's not measurement tool. It's phone with gyroscope which is not calibrated.