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You can do worse than a Fluke. Which one are you getting?<br>
<br>
--TimR<br>
<br>
<div class="moz-cite-prefix">On 12/10/2015 12:47 PM, Dan Snazelle
wrote:<br>
</div>
<blockquote
cite="mid:SNT405-EAS364E7CBE82F30969AB6B9A7C8E90@phx.gbl"
type="cite">
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<div>Thanks guys </div>
<div id="AppleMailSignature"><br>
</div>
<div id="AppleMailSignature">I just ordered my first fluke <br>
<br>
Sent from my iPhone</div>
<div><br>
On Dec 10, 2015, at 2:37 PM, Jason Proctor <<a
moz-do-not-send="true" href="mailto:jason@redfish.net"><a class="moz-txt-link-abbreviated" href="mailto:jason@redfish.net">jason@redfish.net</a></a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<div dir="ltr">fwiw, my Fluke 115 has a special terminal for
measuring up to 10A.
<div><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, Dec 10, 2015 at 11:30 AM,
Dan Snazelle <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:subjectivity@hotmail.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:subjectivity@hotmail.com">subjectivity@hotmail.com</a></a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="auto">
<div>thanks for all the advice</div>
<div><br>
</div>
<div>most multimeters cant measure above 1amp dc
correct? </div>
<div><br>
</div>
<div>i own a few and they only go up to 1amp</div>
<div><br>
</div>
<div><br>
<br>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px">Dan
Snazelle</div>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px"><br>
</div>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px"><a
moz-do-not-send="true"
href="http://SnazzyFx.com" target="_blank">SnazzyFx.com</a></div>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px">and
find us on twitter, facebook and instagram</div>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px">for
tons of my music and some snazzy fx sounds too, </div>
<div
style="font-family:UICTFontTextStyleBody;font-size:19px"><a
moz-do-not-send="true"
href="http://soundcloud.com/loss1234"
target="_blank">soundcloud.com/loss1234</a><br>
</div>
</div>
<div>
<div class="h5">
<div><br>
On Dec 10, 2015, at 11:24 AM, "Doug Forbes" <<a
moz-do-not-send="true"
href="mailto:dougforbes@dslextreme.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dougforbes@dslextreme.com">dougforbes@dslextreme.com</a></a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<div><font face="Arial">How about just get a
digital multimeter from Harbor Freight for
$6 or for free when they have a coupon ?</font><br>
<div> <br>
<div>
<div>
<div> <a moz-do-not-send="true"
href="http://www.harborfreight.com/7-function-digital-multimeter-90899.html"
target="_blank">http://www.harborfreight.com/7-function-digital-multimeter-90899.html</a><br>
<br>
<br>
<br>
</div>
</div>
</div>
</div>
On 12/10/2015 8:07 AM, Richie Burnett wrote:<br>
</div>
<blockquote type="cite">You need to be careful
with grounding if you use a current sensing
resistor and an oscilloscope to measure
current draw from a power supply. For
instance, if both the power supply and
oscilloscope are grounded to the mains
supply earth, and you put the current-shunt
resistor in the V+ feed (high-side sensing)
to measure the current there, then you can't
just connect one oscilloscope probe across
the resistor to measure the voltage drop.
Connecting the scope's ground clip will
short the V+ supply to ground through the
scope, possibly damaging either the scope or
power supply! <br>
<br>
The solutions are: <br>
<br>
1. Power the scope from an isolation
transformer. <br>
2. Use a battery powered "Scopemeter" that
isn't earthed. <br>
3. Run the power supply from an isolation
transformer with it's earth floated. <br>
4. Use a Class-II power supply that isn't
earthed. <br>
5. Use two scope probes to measure the
voltage drop in (Y1-Y2) differential
measurement mode. <br>
6. Move the sense resistor into the 0v line
of the power supply and connect the scope
probe ground lead to the PSU ground side. <br>
<br>
Note, method 6 is only acceptable if the
current flowing in the 0v line is the same
as the current you wanted to measure. This
is fine for something like a single output
+12V power supply, but measuring the ground
current won't work for a multi-output
+5V/-12V/+12V power supply where all of the
wires will likely carry different currents.
<br>
<br>
Hope this helps, <br>
<br>
-Richie, <br>
<br>
<br>
<br>
-----Original Message----- From: Vladimir
Pantelic <br>
Sent: Thursday, December 10, 2015 2:58 PM <br>
To: <a moz-do-not-send="true"
href="mailto:synth-diy@dropmix.xs4all.nl"
target="_blank">synth-diy@dropmix.xs4all.nl</a>
<br>
Subject: Re: [sdiy] measuring dc current
max/draw of psu with a scope or multimeter??
<br>
<br>
On 10.12.2015 15:48, Dan Snazelle wrote: <br>
<blockquote type="cite">im trying to figure
out if this is possible witn regular tools
<br>
<br>
i know i could buy a dc ammeter but those
are expensive <br>
<br>
ive also read about current probes but
some of these seem to saturate at 500ma dc
<br>
<br>
so <br>
<br>
i figured there must be a way to test
current with a resistor and voltage <br>
<br>
<br>
any ideas?? <br>
</blockquote>
<br>
if you put a 0.1 Ohm resistor in-line with
the PSU, then a current of 1A <br>
will give you a voltage of 0.1V that you can
read/measure with the <br>
scope. if the voltage drop is too high, you
can go to a lower resistance <br>
as long as you can reliably measure the
voltage. make sure the resistor <br>
has a tight tolerance e.g. use a precision
shunt. <br>
<br>
<br>
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<pre class="moz-signature" cols="72">--
--Tim Ressel
Circuit Abbey
<a class="moz-txt-link-abbreviated" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a></pre>
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