Measuring low current

[beerbaron]

Hi, I'm trying to measure the average current going to a LED that has PWM (100kHz). I used to use a 10 Ohm resistor and a 100uF cap in parrallel that I would put in line with the LED. Problem is that 10 ohm has too much impact on the circuit, using a smaller resistor like 1 ohm or .1 ohm would be perfect but then, how accurate is a digital multimeter when it come to 100uV to 100mV...

Any suggestions on how I can pull this off. Is there some good products around for my needs? Should I go with an Op-Amp ... I doubt an Op-Amp would be precise enough for uV and low mV ?

Thanks
Frederic

 

[Madcow]

OK, How about two thermal couples,
a resistor (the same as the sense resistor)
with a dc current.
Adjust the current until they read the same
temp.

Ummmm! Beeeeeer!

 

[Skogsgurra]

I think it is time to close this thread. The creativity/reality is getting out of someone's hands...

But I am all for the beer!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Madcow]

Oh, come on Skogs.
Nobody has mentioned "Depth of water sensing".
thread240-58310

LOL

 

[Skogsgurra]

The thread that never died - and never dies...

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...