How to test an LED? [Solved]

[Tekno_Cowboy]

How would you use a multi-meter to make an LED light up? I've done this with my old multimeter, but I can't seem to do it with my new one. I'm hoping that someone here can enlighten me.

I have a Craftsman Professional True-RMS auto-ranging multimeter, if that helps.

 

[Mr Happy]

Re: How to test an LED?

It depends on the meter. Either it will or it won't.

The deciding factor is whether the meter outputs enough voltage to exceed the forward bias voltage of the diode. None of my meters do so.

 

[VegasF6]

Re: How to test an LED?

Which Craftsman is it? I have model 82014. I decided to test the voltage output on the diode test mode. . I set the craftsman to DT and tested the voltage at the leads with a cheap-o meter and read .41 volts out. Then I tried the reverse, cheap-o meter to DT and craftsman to test voltage. Read 2.928V (wow, I will have to be carefull what I probe with this thing). The craftsman would not light the led, the cheap-o would, though very very dimly. I didn't test the voltage under load from the led.

The Craftsman meter doesn't have a diode symbol on it, so I believe it is a continuity test and uses lower voltage than diode test?

.

 

[Tekno_Cowboy]

Re: How to test an LED?

Found the problem. The model 73754 I have only puts out 1.5V for the diode test. I'll have to grab or make an led tester then. Should be a fun project

Thanks!