diode
A diode is the basic electronics component which allows current in one direction and blocks it in the other direction. By construction, a diode is the PN junction and is made of P-type and N-type material.
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.