Re: Motion Sensor Light for Front Entrance

["Josepi" <JRM.@xxxxxxxxxxxx>]

Too funny. I was giving my bunch out to employees for a Christmas gift that
year.
They were all in the electrical energy business so thought they could make
use of them and they were cheap. Better than a bottle?

Non-metering (and then some in the field) people have a hard time with that.
Accuracy eg. 2% of F.S.


"Robert Green" <robert_green1963@xxxxxxxxx> wrote in message
news:i7n7fo$mkg$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Yes, I agree that the Kill-a-Watt is very accurate (matches both tong and
in-line ammeters pretty closely) when measuring gear in the 2A to 15A range.
It's the low end of the scale that's gotten me into a little bit of trouble
before (burned up an XTB based on the bad reading of a mix of inductive and
reactive loads).  To get around it, I built a test box with some banana
jacks and a power cord and outlet that allow me to plug a device into an
inline ammeter without much trouble or fussing with test leads.  I
definitely don't depend on the Kill-a-Watt for accurate readings below 15W
or so.  But it's not really an issue because I have other tools for those
readings.

Since most ammeters have selectable ranges, you can pick the one that's
going to be the most accurate for the current you're trying to read.  The
Kill-a-Watt could be auto-ranging, but I doubt that it is.  It's just
optimized for larger loads than a few watts.  Most people using them are
measuring refrigerators and other large power "hogs."  For that, they're
quite a deal.

Newegg had a sale on the old model when the new ones came out.  They were
about $12 each a while back so I picked up a few for myself and for Xmas
gifts for friends.  Mine are now installed on the window AC, the fridge and
the space heater in the bedroom.  The only issue I have with them is that
they lose their memory when the AC power blinks and it's not practical to
run appliances that large with a UPS.  A battery backup would have been
nice, but I doubt I could get them for $12 each if they had such a feature.
I just have to remember to make note of their readings every now and then,
especially if storms are forecast for the area.

--
Bobby G.

"Josepi" <JRM.@xxxxxxxxxxxx> wrote in message
news:YQyno.3577$sB4.573@xxxxxxxxxxxxxxx
> In the electrical utility field we calibrated most metering devices at
zero
> and 2/3 scale to acheive just what you said.
>
> At 1000 watts I found 4 (units) Kill-a-Watt meters very accurate and
within
> about 0.2% of a lab standard  (traceable) over a fair range of pf. I
cannot
> remeber testing at the low end for the reasons stated above and by R.G.
> below
>
>
> "Robert Green" <robert_green1963@xxxxxxxxx> wrote in message
> news:i7l9lo$fv7$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> The Kill-A-Watt is notorious for not measuring very low wattage devices
> accurately.  My electronic wizard friend theorized that it's because
they've
> optimized their reading range for items people would most likely measure.
>
> I've been fooled by it on a number of occasions.  An in-line amperage
> measurement is likely to show you something different.  Also, the X-10
power
> supplies have a rather unusual design which contributes, I think, to the
> Kill-A-Watt's erroneous readings.
>
> IIRC, a while back Dave Houston (has anyone heard from him?) did some
> measurements that more accurately pegged them at five watts. At the same
> time I put a 7W nightlight and an appliance module connected to a load,
one
> after the other, in a small Styrofoam box and measured the heat rise.  The
> X-10 module warmed the box a slight bit less than the 7w nightlight, but
not
> by half.  There are a couple of threads related to this in Google.
>
> It was a while back and one of the issues was how much heat is generated
in
> the lamp module when it's dimming a very large load.  I know now that a
> 1000W resistive load makes it hot enough to melt into a big blob and lets
> all the magic smoke out.  Experience is gained proportional to the amount
of
> equipment ruined. (-:
>
>  If you were running them "no load" then you also weren't measuring the
> trickle current a plugged in device draws.  I have over 100 modules,
> controllers, AV-switches, telephone responders (one on each light to reset
> the other when either locks up!), meters, loggers, repeaters, transceivers
> and more so I just multiplied 100 by 4 as an average figure.  The rate the
> power meter outside spins when I've shut off all the major loads tends to
> confirm that all my X-10 gear draws more standby current than I wish they
> did.  But even in biology, command and control requires a portion of
overall
> resources and your neurons are consuming tiny bits of energy just waiting
> for a command from the brain.  (-:
>
> If you have an in-line ammeter (the tong meters aren't really suitable,
> either, you might want to revisit the study with loads plugged into a
batch
> of modules.  I'm tempted but my days of doing experiments in the name of
> Usenet are fading.  I've learned that what my wife calls my "science
> experiments"(especially those involving octupussed 110VAC electrical
wiring)
> have VERY low SAF.  The general SAF level seems pegged to the Dow Jones
> average these days.
>
> --
> Bobby G.
>
>
>