FW: Measuring the current draw of a modular

Lahlum-FLR111 Ross ross_lahlum at msmail.wes.mot.com
Mon Mar 10 18:15:05 CET 1997

OOPS! I just realized after thinking about it that if you have a + supply and a
- supply sharing a ground return, the currents from the two supplies will
cancel out in the ground line.  Doh!  So don't do your current measurement in
the ground return... Sorry if I misled anyone.

To: Christopher_List at Sonymusic.Com; synth-diy at horus.sara.nl
From: Lahlum-FLR111 Ross on Mon, Mar 10, 1997 1:51 PM
Subject: RE: Measuring the current draw of a modular


There are a couple of ways to do this.  The first is what you suggested. 
Another way is to get a 0.1 ohm resistor, put it in series with each supply
lead (don't recall how many.. is it one + & one -?), & measure the voltage drop
across it.  Then use ohm's law to calculate the current (I=V/R, or current =
measured voltage/0.1 ohm). Then add up both measured currents.  Another way is
to put the 0.1 ohm resistor in the ground return lead.  Assuming there is only
one gnd return, you'll get all your currents summed up through that branch. 
This would also be a fairly safe place to put a current meter in directly if
you don't want to bother with the 0.1 ohm resistor.

Good luck,

To: synth-diy at horus.sara.nl
From: Christopher_List at Sonymusic.Com on Mon, Mar 10, 1997 1:05 PM
Subject: Measuring the current draw of a modular
RFC Header:Received: by msmail.wes.mot.com with SMTP;10 Mar 1997 13:05:05 U
Received: from ftpbox.mot.com (ftpbox.mot.com []) by
mothost.mot.com (8.7.6/8.6.10/MOT-3.8) with ESMTP id MAA03374 for
<ross_lahlum at msmail.wes.mot.com>; Mon, 10 Mar 1997 12:58:22 -0600 (CST)
Received: from ns1.sara.nl (ns1.sara.nl []) by ftpbox.mot.com
(8.7.6/8.6.10/MOT-3.8) with ESMTP id MAA10994 for
<ross_lahlum at msmail.wes.mot.com>; Mon, 10 Mar 1997 12:58:20 -0600 (CST)
Received: from horus.sara.nl (daemon at horus.sara.nl []) by
ns1.sara.nl (8.8.3/8.7.1) with ESMTP id TAA15230; Mon, 10 Mar 1997 19:48:16
+0100 (MET)
Received: by horus.sara.nl (8.8.3/4.04)
          id SAA59026; Mon, 10 Mar 1997 18:44:20 GMT
Received: from mail1.fw-sj.sony.com by horus.sara.nl (8.8.3/4.04)
          id SAA39053; Mon, 10 Mar 1997 18:44:17 GMT
Received: by mail1.fw-sj.sony.com id KAA00156; Mon, 10 Mar 1997 10:44:19 -0800
From: Christopher_List at Sonymusic.Com
Received: by mail1.nhq.in.sel.sony.com id KAA11146; Mon, 10 Mar 1997 10:44:15
-0800 (PST)
Received: by mailgw1.sonymusic.com(Lotus SMTP MTA v1.05b4 (287.3 12-16-1996)) 
id 85256456.00673112 ; Mon, 10 Mar 1997 13:47:07 -0400
To: synth-diy at horus.sara.nl
Message-ID: <85256456.00671F5D.00 at mailgw1.sonymusic.com>
Date: Mon, 10 Mar 1997 13:49:58 -0400
Subject: Measuring the current draw of a modular
Mime-Version: 1.0
Content-type: text/plain; charset=us-ascii
Sender: owner-synth-diy at horus.sara.nl
Precedence: bulk

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...

- Thanks,

More information about the Synth-diy mailing list