Diode Testing

Most digital multimeters have a Diode setting. This setting is used to test a diode to verify current flows in only one direction.

A good diode will display between 0.4 and 0.8 volt on the meter when the leads are forward biasing the diode, this indicates the diode is allowing current to flow in that direction. When the leads are reversed, the meter should read 1 or OL, indicating the diode is blocking the flow of current in the opposite direction. This indicates a good diode. If the diode allows current flow in both directions or prevents current flow in both directions, the diode is damaged and should be replaced.