Traditionally, speed testing of turntables has been done by viewing a series of bands on the turntable platter under mains lighting. The frequency of the mains supply (50Hz in Europe / 60Hz in the US) causes the bands to appear stationary at the desired speed
Unfortunately mains frequency drifts over time making conventional speed measurement inaccurate. To overcome this problem, companies such as KAB and Clearaudio have produced quartz locked illuminators which work independently of the mains supply to give highly accurate speed readings.
the above was taken from a diy strobe post. It is suggesting that 50/60hz mains freuency is not constant during the day and therefore it is not an accurate test method? If that is the case, doesn't this same phenomenon affect actual speed of the turntable? Perhaps at some times of the day a table will run correct and others not?
In any case, i found this in search of 'stroboscope'. If it is a printout that I would make and hold the incandescent light over it, wouldn'y this have to be done with no stylus running? because a paper template is on top of record.... and does this 50/60 hz fluctuation come into play as well?
Came across this post/mthod , which seems to allow a running stylus during....
the way I calibrate the speed is by playing a record with a 3150Hz testtone on it. The dr Feickert app for android can monitor the sound and an real-time graphical feedback of the speed and the deviation of it. Works like a charm
the method i've used in the past is 100 revolutions/3 mins. Set a timer from online and count revolutions. This can be done with stylus drag. I haven't tried that yet with my AR but I know it is/will measure slow because my ears tell me so...my problem is more how to get the AR speeded up rather than a testing method I think......that is the initial reason I made the post, thinking a speed controller could solve that problem while at the same time, give me some overall fine speed control as well.....