Best way to measure current draw on a +-15vdc supply?

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jwhmca

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Joined
Jan 28, 2009
Messages
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Location
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I have built a small discrete opamp micpre and have one of the channels done. I am wondering what might be the best way to measure the current draw so I can tell how much of a power tranny I will need for say (4) cards?

I thought about just passing the + or - 15 through my fluke, but it seems that would only tell me half the story?
 
A small value resistor in series with each rail (10R) allows you to read the voltage across the resistor and therefore the current draw-

V= I * R

or in this case,

Each 10mV measured represents 1mA

Also, you can leave volt meters attached while you test.

Then take the resistors out when you've tested.

(or add electro's after them to Gnd for post-regulator filtering!)

Use 1% and make sure they have adequate power rating.

Mark
 
For a modest power circuit, the current scale on most VOMs are capable to directly measure the DC current draw. Insert the meter in series with first one power lead (+15v) then the other (-15v).

JR
 

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