Measuring turntable speed

Optimize, in this life it helps to be realistic about things. Nobody I know is going to spend $50 large on a turntable and try to add mass to the platter.
Does a heavy platter reduce wow and flutter? Given the same motor probably but with a different more powerful motor maybe not. One thing I will guarantee is you will never be able to tell the difference. So all this is purely academic. In reality people do just fine with plain A/C synchronous motors and stepped pulleys. The only good reason to have adjustable speed is to match pitch which the vast majority of us do not need. 
I do have a SOTA cosmos with all the fixins and one of the nicest things about it is you can set it and forget about it. I'm not going to add mass to the platter and risk burning out the motor and I do not care about the wow and flutter spec because I can't hear it. Don not burn your brain out mental masturbating about less than trivial issues.  

Just wondering how many turntables you have built??  How many platters of various weights and materials have you tried on the same turntable??  And how about motors and controllers???

Also they use heavy platters with small motors.  But the bearing could be a issue.

Just wondering how you reached a conclusion on what is trivial in audio???

I have a hand held tachometer from China which I trusted but I discovered a moment ago that there is a difference with the arduino from DIY audio of 0.6 turn per minute.