Google isn't being very helpful......it may be that I'm using the wrong keywords. Here are my questions: I'm looking for a device similar to a multimeter that measures amperes and can be plugged into a computer. On the computer, the software needs to provide a graph of the current draw so I can watch it fluctuate in real time. It would also be nice if it calculated things like "RMS" or any other relevant quantities . I have found multimeters than can be connected to a computer, but they only measure up to 10 amps. The various devices I'm connecting to it may draw more. Any help would be appreciated.
http://www.allaboutcircuits.com/vol_1/chpt_8/4.html to increase the current measuring capacity you decrease the the resistance of the shunt. RMS is a voltage variable. voltmeters measure peak voltage. to get RMS multiply the peak voltage by 0.707
What exactly are you trying to measure? The total AC current draw of the power supply, or individual systems within the computer..like the vid card? They do make RMS voltmeters. I used to have a Fluke similar to this: http://www.kiesub.com/prostores/servlet/Detail?no=84 To measure current directly in a DC circuit, you have to open up the circuit and put the meter in series with the load. Unfortunately a clamp-on meter won't work with DC.