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re: "... What is going on here? Â Why is the meter behaving this way?"
I'll take a SWAG (worth what you paid for it): Measuring DC current is
more difficult than measuring AC current, which is usually done with an
inductive pickup. Because DC doesn't create inductance--except
initially--it usually has to be measured inline; i.e. you have to break
the circuit and insert the leads between ends. I suspect the DVM passes
the current through a known-sized resistor, and measures voltage drop.
The DVMs I've seen/used can only measure a few milliamps, anything more
/could/ cause the meter to go bonkers, and just a few milliamps would
take more than a couple days to drain a fully-charged starting battery
(my Mustang has electrical stuff running even when 'off,' and I've gone
several weeks without a dead battery). Again, just a guess.
Bob
On 2/12/2021 4:52 AM, jim via Healeys wrote:
> not helping on meter question, but 12 volt lights with clip-leads
> attached will show current flow quite nicely....remove fuse...clip
> light bulb across removed fuse...if circuit is conducting current, the
> light bulb will "glow"Â Â Â (simetimes called a "bug-lite" by the old
> Telephone Company Central-Office-Techs)
>
>
> Jim
>
> On Wednesday, February 10, 2021, 4:04:57 PM PST, llennep--- via
> Healeys <healeys@autox.team.net> wrote:
>
>
> Hello Listers,
> I am seeking to tap the knowledge of the list on this general auto matter.
> I bought a hot rod last year and from the get go I have had a battery
> drain. Â If system is left on the batt will get too weak to start
> engine in a couple days or so. Â Recently I have been chasing the
> problem in earnest. Â I did find one issue and resolved that with the
> hope that the drain was fixed. No. Â Still there.
> So yesterday I began preparing for the standard search method -
> pulling fuses one at a time and noting the drop in amps running
> through the system. Â However I needed a dependable multimeter. Â I have
> 3 but do not trust the amperage reading on any of them. Â I secured a
> known good meter today and here is what I am observing.
> The reading starts out reading a few tenths amp fluctuating wildly and
> then drops to almost 0 in 2-3 seconds. Â This happens time after time.
> Â What is going on here? Â Why is the meter behaving this way?
> Any help much appreciated.
> Keith
>
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re: "... What is going on here? Â Why is the meter behaving this
way?"<br>
<br>
I'll take a SWAG (worth what you paid for it): Measuring DC current
is more difficult than measuring AC current, which is usually done
with an inductive pickup. Because DC doesn't create
inductance--except initially--it usually has to be measured inline;
i.e. you have to break the circuit and insert the leads between
ends. I suspect the DVM passes the current through a known-sized
resistor, and measures voltage drop. The DVMs I've seen/used can
only measure a few milliamps, anything more <i>could</i> cause the
meter to go bonkers, and just a few milliamps would take more than a
couple days to drain a fully-charged starting battery (my Mustang
has electrical stuff running even when 'off,' and I've gone several
weeks without a dead battery). Again, just a guess.<br>
<br>
Bob<br>
<br>
<br>
<div class="moz-cite-prefix">On 2/12/2021 4:52 AM, jim via Healeys
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1992481377.821668.1613134320693@mail.yahoo.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div class="ydpc1c799e1yahoo-style-wrap" style="font-family:
Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 13px;">
<div dir="ltr" data-setdir="false">not helping on meter
question, but 12 volt lights with clip-leads attached will
show current flow quite nicely....remove fuse...clip light
bulb across removed fuse...if circuit is conducting current,
the light bulb will "glow"Â Â Â (simetimes called a "bug-lite"
by the old Telephone Company Central-Office-Techs)<br>
</div>
<div dir="ltr" data-setdir="false"><br>
</div>
<div dir="ltr" data-setdir="false"><br>
</div>
<div dir="ltr" data-setdir="false">Jim<br>
</div>
<div><br>
</div>
</div>
<div id="ydpccfe006cyahoo_quoted_3834172358"
class="ydpccfe006cyahoo_quoted">
<div style="font-family:'Helvetica Neue', Helvetica, Arial,
sans-serif;font-size:13px;color:#26282a;">
<div> On Wednesday, February 10, 2021, 4:04:57 PM PST,
llennep--- via Healeys <a class="moz-txt-link-rfc2396E"
href="mailto:healeys@autox.team.net";><healeys@autox.team.net></a> wrote:
</div>
<div><br>
</div>
<div><br>
</div>
<div>
<div id="ydpccfe006cyiv2638515020">
<div style="color: black; font-style: normal; font-weight:
normal; font-stretch: normal; font-size: 10pt;
line-height: normal; font-family: arial;
font-size-adjust: none;">Hello Listers,<span></span>
<div>I am seeking to tap the knowledge of the list on
this general auto matter.</div>
<div>I bought a hot rod last year and from the get go I
have had a battery drain. Â If system is left on the
batt will get too weak to start engine in a couple
days or so. Â Recently I have been chasing the problem
in earnest. Â I did find one issue and resolved that
with the hope that the drain was fixed. No. Â Still
there.</div>
<div>So yesterday I began preparing for the standard
search method - pulling fuses one at a time and noting
the drop in amps running through the system. Â However
I needed a dependable multimeter. Â I have 3 but do not
trust the amperage reading on any of them. Â I secured
a known good meter today and here is what I am
observing.</div>
<div>The reading starts out reading a few tenths amp
fluctuating wildly and then drops to almost 0 in 2-3
seconds. Â This happens time after time. Â What is going
on here? Â Why is the meter behaving this way?</div>
<div>Any help much appreciated.</div>
<div>Keith</div>
</div>
</div>
<br>
</div>
</div>
</div>
</blockquote>
<br>
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