When checking a diode for an open or short circuit, what is the proper procedure?

To properly check a diode for an open or short circuit, disconnecting it from the circuit is essential. This step ensures that you are assessing the diode's functionality without interference from other circuit components. When a diode remains in the circuit during testing, the readings can be misleading because current can still flow through other paths, which may mask the actual condition of the diode itself.

Using a multimeter to check a diode after disconnecting it allows for an accurate measurement of its health. A functioning diode will show low resistance in one direction (forward bias) and high resistance in the reverse direction. If the diode is open, it will show high resistance in both directions, and if it is shorted, it will show low resistance in both directions. These clear readings can only be obtained when the diode is isolated from the circuit.