dmm question

is it possable to use a dmm to see how much watts your amp is putting out?
or do you have to use an o-scope

Im not 100% sure, i always though you could put the leads to the pos/neg of the amp and read them as amps, and do the formula to get the power your putting out.

putting the leads to the positive and negative will yield a voltage reading, to read current the meter must be in series .... i.e. you disconnect one the speakers leads and connect the speaker wire to one of the DMM leads, the other DMM lead is connected to where the speaker lead was connected to the amp.

The first method is acceptable and the easier of the two, the formula is: Power = Volt^2/R. Remember to set the DMM to Volt AC .... NOT DC.

/\/\/\yep he's right

Thank you for making how its done clear, iver tried it but it didnt work so now i know why.

and if you try to hook up a regular dmm in series to find amperage draw, you will most likely fry your dmm. most can only handle around 10 amps.

putting the leads to the positive and negative will yield a voltage reading, to read current the meter must be in series .... i.e. you disconnect one the speakers leads and connect the speaker wire to one of the DMM leads, the other DMM lead is connected to where the speaker lead was connected to the amp.

The first method is acceptable and the easier of the two, the formula is: Power = Volt^2/R. Remember to set the DMM to Volt AC .... NOT DC.


thanks i will be sure to try it when i buy a dmm tomorrow. now what is something to look for when looking for a dmm to do that plus set gains and stuff like that.

nothing special is needed .... a $20 walmart special should suffice

This is the one i got

http://cgi.ebay.com/VELLEMAN-DVM850BL-3-DMM-10A-Digital-Multi-Meter_W0QQitemZ180078270091QQihZ008QQcategoryZ7315 8QQtcZphotoQQrdZ1QQcmdZViewItem

Im going to start saving up for one with an o-scope.

I installed a 60amp gauge in my dash dedicated to the amp. That way I can see what I'm pulling all the time. So far I've got it up to 45 amps continuous. On 10gauge wire, that's pushing it....

I installed a 60amp gauge in my dash dedicated to the amp. That way I can see what I'm pulling all the time. So far I've got it up to 45 amps continuous. On 10gauge wire, that's pushing it....


can you fry a egg on the amp yet?

oh and paulD that is voltage square right.

heh heh, you could until I mounted a 80mm 72cfm fan out of a PC on it. It's loud as hell, though. I try to keep it around 30amps with a tight bass hit.

yes .... X^2 is X squared

pimp, why do you need an o'scope ?

Just to have one, never know when you will need it and i can get one for about 150. I dont have a reason why and i do all my tuning by ear.

:) i need one too.

I've got two, and both are old tube-type. And they work!

My grandfather has a few, but i like something you carry around without lugging it.

Yeah, both of mine weigh about 20 lbs..

the new high speed digital ones have finally caught up with the very best from like 20+ years ago - they had plug-in modules.