Multimeters
An overview of what multimeters are, how they work, and what they can measure can be found at: http://www.sciencebuddies.org/science-fair-projects/how-to-use-a-multimeter.shtml#multimeteroverview
Oscilloscopes
An overview of what multimeters are, how they work, and what they can measure can be found at: http://www.sciencebuddies.org/science-fair-projects/how-to-use-a-multimeter.shtml#multimeteroverview