Can diodes be checked while the power is on in the circuit?

Diodes should not be checked while the power is on in the circuit because doing so can pose several risks. When power is applied to the circuit, there is potential for incorrect readings, as the normal operating conditions can influence the diode's behavior. Furthermore, testing a diode in the powered state could lead to damage not only to the diode but also to the testing equipment being used.

Checking diodes while power is off allows for the application of a known forward voltage without interference from other circuit elements. This controlled testing environment ensures an accurate assessment of the diode's functionality, whether it's in terms of forward voltage drop or reverse leakage current. Therefore, working with the power off is the safest and most reliable method for testing diodes.