I bought a gadget from DHGate.com. It is a laser RPM reader. You stick a piece of reflective tape to the platter and point the laser at it and you will get an accurate reading. It cost something like $15 shipped.
I've since just leave the tape on the platter, so I can check the speed from time to time.
FrankC
I've since just leave the tape on the platter, so I can check the speed from time to time.
FrankC