I decided to test some diodes that I have, using a multimeter to measure their forward bias voltage. I set my multimeter to voltage test and connected the diode across:
I tested a bunch of different diodes, both germanium and silicone type, so I expected to see voltages around 0.2 – 0.7V. However, all diodes showed 0V!
I tried reversing the polarity of the diodes, as well switching multimeters. Always my measurement came out as 0V. So am I making some kind of mistake in measuring diodes, or are both of my multimeters/all diodes broken?
Best Answer
In voltage mode, a multimeter just measures what voltage is present between its leads. What you want is diode test mode, which is usually indicated on the dial with a diode symbol. On your meter, it's the option one to the left of your voltage mode--set the dial to that and press the mode button a few times to put it in diode mode; it'll say on the LCD. In diode mode, the meter applies a known current to the diode -- you can check the meter's datasheet or instruction manual to know what current it uses, and fancier meters might even let you select a current -- and then measures the voltage across the diode.
Note that this usually won't work for LEDs, as most meters limit their diode test voltage to only one or two volts, which is too low to turn on any LEDs except maybe some red or yellow ones. But for a conventional diode like the one you show in the picture it will work fine.