When testing diodes with an ohm meter, what reading indicates a good diode?

A good diode exhibits the characteristic of allowing current to flow in one direction while blocking it in the opposite direction. This behavior is fundamental to how diodes function in circuits, which is to control the direction of current flow.

When testing a diode with an ohm meter, a reading that shows low resistance in one direction indicates that the diode is conducting properly, allowing current to pass through. Conversely, a high resistance reading in the opposite direction confirms that the diode is functioning as it should, as it prevents current from flowing the wrong way.

The other readings might indicate issues: low ohms in both directions would suggest a short or failed diode, high ohms in both directions could indicate an open diode, and high ohms in one direction and low ohms in the other does not fully encapsulate the proper functioning of a diode in a clear manner. Therefore, the characteristic of showing a clear directional flow of current—low resistance in one direction and high resistance in the other—is what defines a good diode.