Measuring the current draw of a modular

[gstopp at fibermux.com]

     Having blown up a bunch of stuff in my time maybe I can give you some 
     pointers....
     
     Uh okay maybe that sounds scarier than it should - it's not all that 
     dangerous - the thing that is in the most danger during power supply 
     current measurements is probably your meter.
     
     Before you do anything you should have a reasonable idea in your head 
     about how much current you'll be measuring, like "under two amps" or 
     "over two amps". Start with your meter on the highest current setting 
     (assuming you have a normal meter, not something that could withstand 
     an arc-welder). Usually this is like ten amps. You will probably have 
     to move the red lead into a special (fused) hole for this. When you 
     dial in "DC-A" or whatever, be sure to select the range that matches 
     the high-current hole.
     
     Put the meter in series with the DC power line, like you say. Don't 
     let it slip free and swing around and spark against everything in 
     reach - this is how stuff gets fried. Gets the adrenaline going too.
     
     If the current turns out to be within a lower range, then move to the 
     lower range because your reading will be more accurate. Make sure you 
     move the test leads at the meter as required.
     
     Okay here is the part to remember - don't leave the meter lead in the 
     amps hole! If you do then you will probably forget and the next time 
     you use the meter you will probably measure a power supply voltage 
     first and if you do that with the test leads in the amp position you 
     will drop a bunch of volts *across* the meter (rather than through it) 
     and it will fry. It's not really fried, of course, they put fuses in 
     the amp holes just for dopes like me. The frustration comes when you 
     need to find a replacement fuse without getting in you car and driving 
     to the electronics store.
     
     Hope this helps.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Measuring the current draw of a modular
Author:  Christopher_List at Sonymusic.Com at ccrelayout
Date:    3/10/97 11:01 AM
     
This may seem like a silly question - but how do you guy recommend 
measuring the current draw of your modular?
     
Do you just snip the positive voltage line, strip it and run it through 
your multimeter via alligator clips?
     
Is this safe?
I'm scared :).
I don't want to fry a whole mess of chips by turning on only half of the 
power supply...