Reading Between the Lines
3. Interpreting Resistance Readings
Okay, so you've got your multimeter set to measure resistance. You've connected the leads to the diode in both directions. Now what do those numbers mean? Well, in the forward direction (positive to anode, negative to cathode), you should see a low resistance reading. How low? That depends on the diode, but generally, anything below a few hundred ohms is considered a good sign.
In the reverse direction (positive to cathode, negative to anode), you should see a very high resistance reading — ideally, something in the megaohm range or even "OL" (overload) on your multimeter display. This indicates that the diode is effectively blocking the flow of current in that direction. If you see a low resistance reading in both directions, the diode is likely shorted and needs to be replaced. It's like a door that's supposed to be locked, but someone left the key in the lock.
It's important to remember that these are just general guidelines. The exact resistance readings you get can vary depending on the type of diode, the temperature, and the specific multimeter you're using. However, the key takeaway is that there should be a significant difference in resistance between the forward and reverse directions. A healthy diode will have low resistance in one direction and very high resistance in the other.
So, don't get too hung up on the specific numbers. Focus on the difference between the readings. If you see a clear difference, the diode is likely working as it should. If you see similar readings in both directions, or if the readings are very low in both directions, then it's time to start shopping for a new diode.
