# Simple LED circuit question

Got a question regarding a simple circuit. 9v battery to 470? resistor to led to ground. running a multimeter in series I'm getting amperage but no light from the LED. Its been a while since I've messed around with my electronics and I'm a little rusty but isn't the meter in amperage just like a jumper wire? Thanks for the help!

Sounds like the LED is round the wrong way.

You also might have the multimeter on voltage and not amperage. I'd also suggest taking the multimeter out of the loop.

Oh, and the longer lead of the LED is positive.

sorry I forgot to say the circuit works normal with the multimeter out of series and the led lights. It just wont light with my meter in series, but it will read amperage. If the cathode was facing power I wouldn't be getting any measurement since the circuit wouldn't be complete.

Sounds like you have the multimeter probe connected to the wrong terminal.

Usually they have 3 (or 4) terminals:

Amp () GND () Volt ()

To use it an an ammeter, you have you connect the red wire to the Amp terminal (sometimes marked as 'A'), and the black wire to the GND (or Comm/Common/COM) terminal.

Some have 4 terminals, usually the fourth is for higher current loads. Mine for example has 4 terminals: 10A,A,COM,V

It will be reading voltage when you have it in series otherwise. If you connect the LED backwards, it is reverse biased, and the multimeter will see no voltage (as the multimeter requires a tiny amount of current to read the voltage).

If the cathode was facing power I wouldn't be getting any measurement since the circuit wouldn't be complete.

Yes you would. LEDs have a reverse bias leakage current and depending on the LED can sometimes have a reverse breakdown voltage of 5V. So you would see current if you had it the wrong way round.

sorry I forgot to say the circuit works normal with the multimeter out of series and the led lights. It just wont light with my meter in series, but it will read amperage.

Then as mentioned above you have not got your meter switched to amps correctly.

Grumpy_Mike: Yes you would. LEDs have a reverse bias leakage current and depending on the LED can sometimes have a reverse breakdown voltage of 5V. So you would see current if you had it the wrong way round.

Connect a 'Voltmeter' in series with a 9v battery, and a reverse biased LED. You'll see what I was meaning.