Ross said:
This was not a post about a single PC or how to wire a branch circuit....
Oh. I thought you were trying to discuss something
relevant to this thread. Since that part of your post
was not intended to relate to the thread, that part is
irrelevant - as I stated. The RMS point, however, is
completely relevant.
Do you think your $2.99 dmm is any more accurate than the cheap amp > clamp...
I'll answer below - but since you have chosen to
go with a meter that is not capable of true RMS
readings, neither approach is acceptable.
If you read what I posted, you would have seen that
I do think it is equivalent. Its specs are better -
1.2% for the DMM, 2% for the clamp on. As shown, its
price is about one fourth of the Ebay meter you
mentioned: $2.99 vs $12.99, or $5.94 vs $22.98 when
you include shipping. To make the resistor "box"
modify a $2.88 power strip (see below - watch the line
wrap:
http://www.electronix.com/catalog/product_info.php/cPath/14_60/products_id/6919
with a precision resistor $5.01 plus (estimated)
$6.00 shipping from Mouser.
Total cost: $5.94 + 2.88 + $5.01 + $6.00 = $19.83
Show me a line of good DMM's and Amp Clamps where the clamps are more
expensive than the DMM...
A Fluke 335 (true-RMS clamp meter) lists for $194.00
at test Equipment Depot. The Fluke 110 true-RMS DMM
lists for $109 there. Same prices at Mouser. The 335
spec for the 0-400A scale is 2% +/- 5 counts. The AC
voltage spec accuracy for the 110 is 1%
As far as I know, all of them (good true-RMS amp clamps)
are more expensive than the good true-RMS DMM + precision
resistor approach for measuring PC current draw to the
same degree of accuracy. I was hoping you would correct
me on that, which was why I asked.
maybe I will learn something "in your own words"
Well, I'd be a whole bunch happier if you would
show me where I'm wrong about the price.
Also, where are you going to mount your 20 watt resistor??? Just dangle in
on a lamp cord???
Answered already. Put it in a power strip. Or use
the project box, as you suggest, or a j-box.
It's "do-able" in-line in a cord, but I would not
advise that.
I have referred to the op many times in my
responses to you, even quoting from that post.
I'm not here to argue - your question strikes
me as having argument in mind. I'm here because
there is a disagreement in methods, and there is
always the possibility that a different method
is better than the method I have in mind. Obviously,
I believe the resistor/DMM method is better. I've
tried to make my thinking on that clear, so that you
or someone else can point out where I am wrong.
That can only help me. You have already demonstrated
that, by pointing me to a clamp-on for $23.00.
I did not know you could get one for that little.
You think you and DarkMatter are giving good advice to someone who would
even have to ask that question?
Another apparently argumentative question which
doesn't help the discussion. Can we please avoid
that? I would not knowingly post what I thought
was bad advice. So far, what I said has not been
disproved. I do not agree with using a clamp on
or DMM that does not include true-RMS capability
for this measurement. But even if you do, it costs
less with the resistor/DMM approach. That has not
been disproved - I've posted numbers and references
to support it. I've posted what you asked for - a
price comparison of good (Fluke) true-RMS meters of
both varieties - clamp on vs DMM. That is where
I hope you will prove me wrong. It's your question,
rephrased swapping clamp-ons with DMM's:
"Show me a line of good DMM's and Amp Clamps where
the" DMM's "are more expensive than the " clamp on's...