<snip>

> Try one of these and your multimeter:
>
> http://www.analog.com/en/subCat/0,2879, ... 5F,00.html
>
> First, use one to measure the RMS current into the DUT, then the RMS
> voltage across it, then multiply the two readings and you'll have
> the power your DUT is dissipating.
> ---

<snip>

How do you account for phase errors, for instance when your DUT is a
transformer?

petrus bitbyter

Bob Monsen says...

> Bob Pease has a good article about how a watt meter
> works, and a working schematic.

> http://electronicdesign.com/Articles/In ... ?AD=1&Arti
cleID=2190

Thanks, Bob, but I'm unable to get to the site. I just get
an unending series of ads. It says "Click here to go to
electronic design, or wait 20 seconds." But no matter what
I do, I just get the same ad and another countdown, and
another "AD=1" added to the end of the address.

Nevermind. They want cookies.

Bob Monsen says...

> OTOH, I concur with the folks who say a Kill-A-Watt is
> the way to go. Much more reliable, less dangerous, and
> quite fun.

I Googled:

kill-a-watt accuracy

and this Anandtech thread came up first:

http://forums.anandtech.com/messageview ... id=2147352
&enterthread=y

which compared Kill-a-Watt readings for various things with
readings on the same items from a Fluke 1735, which I gather
is a VERY expensive watt meter, with not particularly good
results. Included was:

> Its not accurate at measurements of small wattages.
> Things like the power usage of a dvd player in standby
> mode are not accurate. Killawatt said dvd player was
> using about 5 watts, fluke 2.64 watts.

Of course, even if it's wrong, it could still be useful if
it's consistently wrong - if I could apply a fudge factor of
some kind.

Anyway, I accept that the answer to my original question -
can I get good measurements with a simple home-brew ciruit -
is no, that doesn't work.

On Sun, 17 Feb 2008 15:18:03 +0100, "petrus bitbyter"
<pieterkraltlaatditweg@enditookhccnet.nl> wrote:

><snip>
>
>> Try one of these and your multimeter:
>>
>> http://www.analog.com/en/subCat/0,2879, ... 5F,00.html
>>
>> First, use one to measure the RMS current into the DUT, then the RMS
>> voltage across it, then multiply the two readings and you'll have
>> the power your DUT is dissipating.
>> ---
>
><snip>
>
>How do you account for phase errors, for instance when your DUT is a
>transformer?

---
Aaarghh!!!!

What _was_ I thinking???

Thanks.

--
JF

On Sun, 17 Feb 2008 09:34:28 -0600, George <gh424NO824SPAM@cox.net>
wrote:

>Nevermind. They want cookies.

Download Opera and set it to discard ALL cookies at the end of a
browser session.

Hmmm. Just tried the link and it counted *past* zero but eventually
got to the article. Another MSIE-wired site?

--
Rich Webb Norfolk, VA

Rich Webb says...

>> Nevermind. They want cookies.

> Download Opera and set it to discard ALL cookies at the
> end of a browser session.

> Hmmm. Just tried the link and it counted *past* zero but
> eventually got to the article. Another MSIE-wired site?

I had session cookies enabled in IE7, but that wasn't
enough. But when I added it to the allowed sites for hard
drive cookies, it went right through. What was confusing
was that usually a site will say at some point if cookies
are required. This one didn't.

I don't want to discard all cookies. Some of them keep
track of where I left off, and are useful. But I allow the
specific sites I need, and just allow 1st party session
cookies on everything else.

On Sun, 17 Feb 2008 15:24:24 -0600, George <gh424NO824SPAM@cox.net>
wrote:

>Rich Webb says...
>
> >> Nevermind. They want cookies.
>
> > Download Opera and set it to discard ALL cookies at the
> > end of a browser session.
>
> > Hmmm. Just tried the link and it counted *past* zero but
> > eventually got to the article. Another MSIE-wired site?
>
>I had session cookies enabled in IE7, but that wasn't
>enough. But when I added it to the allowed sites for hard
>drive cookies, it went right through. What was confusing
>was that usually a site will say at some point if cookies
>are required. This one didn't.
>
>I don't want to discard all cookies. Some of them keep
>track of where I left off, and are useful. But I allow the
>specific sites I need, and just allow 1st party session
>cookies on everything else.

What I do in that case, and for sites where the cookie contains login
credentials, is click to the cookie list (tools | advanced | cookies)
and set the ones that I want to keep to be retained.

If you haven't tried Opera (or Firefox) give it (them) a whirl.

--
Rich Webb Norfolk, VA