Voltage Source
A voltage source is a two terminal device providing a constant voltage across its terminals regardless of current flowing through it. A voltage source may be dependent on some circuit variable or may be independent at all.
3 Methods of testing a diode with multimeter and oscilloscope
Testing a diode with a digital multimeter in two ways, diode testing portion, and ohmmeter. A diode test is considered passed if it shows low resistance/voltage drop on forward bias and high resistance/voltage drop in reverse bias. A diode curve tracer uses an oscilloscope for VI characteristics graph.