Get a volt meter (DMM; Cheap-o from Wal-Mart is like ~$12), set it to read DC voltage, and place the positive lead on the power terminal/wire then place the negative lead on the ground terminal/wire
Get a volt meter (DMM; Cheap-o from Wal-Mart is like ~$12), set it to read DC voltage, and place the positive lead on the power terminal/wire then place the negative lead on the ground terminal/wire