Effin' ripple

roothorick

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I really have to challenge the common wisdom of checking for ripple with a multimeter set to AC. I think most meters won't produce good values when in AC mode probing DC.

I've tried two different meters on a power supply I'm pretty sure is good... One goes "OL" for a second, then counts down from 16, and then repeats. The other gives me a constant 10V reading (I'm checking 5VDC). I frankly don't trust either.

IMO, to check for ripple, you'll need a scope... Well, a speaker might do in a pinch.
 
You really need an analog meter or scope to do that right... Digital meters are t3h suck for it.

Besides, you aren't measuring 50/60 cycle AC but the full wave rectified AC that isn't fully filtered.
 
My Fluke gives good AC ripple readings. A couple of times I've looked at it with the scope too, and it's pretty much right on (the visually-estimated RMS value).

I'll try some of my cheapo DMMs and see what I get...
 
My Fluke gives good AC ripple readings. A couple of times I've looked at it with the scope too, and it's pretty much right on (the visually-estimated RMS value).

I'll try some of my cheapo DMMs and see what I get...

Well, Fluke would be the brand to get it right, but with this cheap crowd I don't expect many people to have a Fluke meter. :)
 
You really need an analog meter or scope to do that right... Digital meters are t3h suck for it.

Besides, you aren't measuring 50/60 cycle AC but the full wave rectified AC that isn't fully filtered.

The meter that gave 10V was an analog. Maybe it's only certain meters.

I have a project involving acquiring oscilloscopes about to get underway, so I'll have a scope soon enough.
 
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