Kill a Watt(tm) power meters

Posted by Mark Lloyd on October 30, 2009, 8:29 pm

wrote:

>> That would be fine. The problems are when you keep CHANGING it.
>> Maybe you realize that DST all the time is the same as no DST at all.
>> Clocks are an hour different, but we'd adapt to that. There'd just be
>> no changes to keep messing things up.

>Close, but not exactly. DST gives me (in winter) a dark morning and light
>driving home in the evening.

Getting up earlier and leaving work earlier is what does that.

>Standard time gives me more light in the
>morning and I drive home in the dark.

Getting up later and leaving work later does that.

>My preference is to function on the
>same time as DST.

Meaning you'd like to do things later in the day. Apparently, a lot of
people feel like that.

> If I was on the opposite side of my time zone, I'd be
>rather close to what DST is here. My preference is to have the winter dark
>in the AM. I did that by changing my hours at work but the rest of the
>world does not seem to want to comply to my personal choices for everything.
>People often state a preference, but that may not be the same as we see it
>in different parts of the same time zone or the northern versus southern
>latitudes. At work I have the luxury of coming and going as I please, but
>most do not.

That's good. Do it as you please. That's a lot better that supporting
this mind game that claims to alter time, but does not (and can not)
do such a thing.
--
56 days until the winter solstice celebration

Mark Lloyd
http://notstupid.us

"How could you ask me to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

Posted by Mark on October 28, 2009, 11:19 am

> You can get a "clip on" multimeter from harborfreight.com =A0(free
> catalog) for about
> $10.00 and measure the current consumed by the device by simply
> clipping around
> one of the wires (usually the black one) going to the device, and it
> will work for any
> device that works on 60 cycle AC. =A0The current, times 120, is the kva
> in watts.

In an AC circuit, Volt x Amps are not exactly the same thing as Watts
due to power factor.

For loads like incandesenct light bulbs and resistance heaters, the
power facotr is very close to one so there is little error but for
reactive loads like motors, there can be a significant difference.

Mark

Posted by bud-- on October 28, 2009, 1:12 pm

Andy wrote:

>> Anybody familiar with them? Is the "EZ" (model P4460) worth an
>> extra $15 over model P4400?
>> I want to see how much electricity my freezers, TV sets, computers,
>> etc are *really* using, plus check the frequency stability of my
>> portable generator and that little inverter than I mounted in my truck.
>> Thanks,
>> Bob

>
> Andy comments:
>
> I'd like to suggest an alternative.
>
> You can get a "clip on" multimeter from harborfreight.com (free
> catalog) for about
> $10.00 and measure the current consumed by the device by simply
> clipping around
> one of the wires (usually the black one) going to the device, and it
> will work for any
> device that works on 60 cycle AC. The current, times 120, is the kva
> in watts.

You will get the VA, not the watts. They are not the same except for a
pure resistance load like a light bulb. They are not the same because of
"power factor". If you want the cost of using anything with a motor you
need to know the watts.

Posted by Ed Pawlowski on October 28, 2009, 10:01 pm

> I'd like to suggest an alternative.
> You can get a "clip on" multimeter from harborfreight.com (free
> catalog) for about
> $10.00 and measure the current consumed by the device by simply
> clipping around
> one of the wires (usually the black one) going to the device, and it
> will work for any
> device that works on 60 cycle AC. The current, times 120, is the kva
> in watts.
> A simple calc yields the cost per hour to run it.

The advantage of a Kill a Watt meter is that it records over time. It takes
fluctuating load into consideration, especially important on refrigerators
and freezers that have a varying load over time, from nothing to full power
with compressor and defrost equipment in use. A spot check will not give
the complete story. Also, no splitting of the cord is required.

Your system works well with simple load that are constant when on.

Posted by Dan Musicant on November 1, 2009, 4:09 pm

:Anybody familiar with them? Is the "EZ" (model P4460) worth an
:extra $15 over model P4400?
:
:I want to see how much electricity my freezers, TV sets, computers,
:etc are *really* using, plus check the frequency stability of my
:portable generator and that little inverter than I mounted in my truck.
:
:Thanks,
:Bob

Two things:

I.

I bought the P4400 in February of 2008. I left it plugged into a power
strip and plugged my desktop computer's power strip (and etc.) plugged
into the Kill-a-Watt meter, measuring power draw (watts), for an
indefinite time. It stopped working. It came back to life, don't
remember the details, but leaving it off and unplugged for a while, it
started working somehow. Someone said they thought that the meters
aren't designed to be used in this way, so I stopped doing it.

II.

I've found that the P4400 (don't know about the other(s)) doesn't
measure low power draw at all accurately. IOW, if your device is drawing
3-4 watts, say, the P4400 doesn't give you anything like an accurate
reading. I only know this because I have a far more accurate way of
measuring power draw, which I have used for years. The P4400 is a lot
easier to use, but my system is much more accurate and I feel I can
depend on it more. It's a simple thing I put together for next to
nothing:

1. I already had a decent digital multimeter that measures AC amps,
easily converted into watts (amps x 120 volts = watts). It cost me
around $100 in the early 1990's.

2. I bought a couple of banana plugs that will fit in the multimeter's
input jacks and attached them to a length of AC two conductor cord,
around 6 feet long. The other end of this ~6 foot length of cord is
soldered (both leads) to either end of a cut wire in a short extension
cord. IOW, I cut one wire in the middle of that extension cord and
connected the cut ends to the cord, the other end of which has the
banana plugs. Plugging the banana plugs into the multimeter first
(ALWAYS do it this way or you will likely cause a dangerous short !), I
THEN plug the extension cord into a power outlet and then a device into
the female end of the extension cord. The multimeter gives me the
current draw and simple arithmetic gives me the watts. Amps x 120 =
watts.

Using this system I determined that the P4400 is useless for low draw
measurement. I don't remember the cutoff where the P4400 starts being
useful. I assume that this holds true for all of them and that I don't
have a lemon here.

Dan

Email: dmusicant at pacbell dot net

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Kill a Watt(tm) power meters - Page 8