The best way to demonstrate cogging is to spin the platter by hand, apply stylus to vinyl, and notice the sound. Then engage the motor. If the sound deteriorates in clarity or shows increased high frequency content, you have demonstrated cogging. Obviously engaging the motor will improve pitch consistency.
If you can't demonstrate cogging, it may be because of bearing noise - the bearing is so noisy that it swamps cogging noise. An air bearing TT is capable of resolving even tiny amounts of cogging, which I can hear clearly with a 1.8W multiphase motor driven by an adjustable, precision supply. For the significance of this, read Phoenix above.
If you can't demonstrate cogging, it may be because of bearing noise - the bearing is so noisy that it swamps cogging noise. An air bearing TT is capable of resolving even tiny amounts of cogging, which I can hear clearly with a 1.8W multiphase motor driven by an adjustable, precision supply. For the significance of this, read Phoenix above.