If the generator is polarized and spun without any wires connected, the "residual voltage" between the "F" terminal and the generator housing (ground) will be approximately 1/2 Volt DC. The "Arm" terminal will have approximately the same reading until the "F" terminal is grounded, then it will spike to 20 volts or more, depending on the speed of the armature. It's much better to use an analog meter with a sweep needle instead of a digital meter when working with a DC generator and a 3-unit magnetic regulator. Digital meters are too sensitive to voltage spikes and "noise", resulting in unintelligible gibberish instead of a good reading.
To get a good test, a battery, an ammeter, and a voltage regulator will need to be wired in to simulate a complete charging system.
Jerry
