An oscilloscope can be used to accurately measure the rotational speed of a drill press or other workshop tool.
Step 1: Coil
Coil a wire around a nail.
Step 2: Magnet
Attach a magnet to the drill chuck. Set the coiled wire parallel to the magnet and hook up to the oscilloscope.
Step 3: Scope
When the magnet passes the wire it will create a small current that will appear on the scope.
Clocking 7.3 divisions at 5ms per division. 7.3 x 0.005 = 0.0365 seconds per revolution.
1 / 0.0365 = 27.4 revolutions per second.
27.4 x 60 = 1644 revolutions per minute.