On Aug 13, 7:38 am, Arno Wagner wrote:

The transformer - if that's the correct term for it - big gray
basically cylindrical unit on top of a power pole - near my house blew
once.

Ugh. Putting them up for each individual hous is a very, very
historic way to do it.


I don't think there's one by every house, seems like you see them
every few poles.


The right way to do this is to use bigger transformesr for 10-100 houese
and to bury 3-phase AC lines. A lot more expensive, but pays off
in the long run, since you have less problems. And all these ugly
poles and transformers will vanish.


I know the power lines coming into my house are definitely above
ground. They're strapped to a supporting cable coming from a power
pole.

On Aug 13, 12:32 pm, kony wrote:

The price is all wrong. Nobody can build a decent product with
these specs for that price. You cannot even buy the components
needed in decent quality for that price.

Depending on your definition of "decent", this may be true,
but it's going to be roughly equivalent to what you'd buy
from APC as a 500VA for about $50 so if that's what the
budget allows, it's not an exceptionally low price (also
considering you can sometimes get the APC discounted or with
rebate putting it closer to $20-30 than to $50.


FWIW, I was in that same Best Buy today and the UPS model I got for
$69 was back to its normal price of $119.

Ugh. Putting them up for each individual hous is a very, very
historic way to do it.


I don't think there's one by every house, seems like you see them
every few poles.


Generally it's 4-10 houses per transformer, it's nice, it makes it possible
to have quite good voltage regulation. I rarely see mine change by more than
a volt plus or minus.


The right way to do this is to use bigger transformesr for 10-100 houese
and to bury 3-phase AC lines. A lot more expensive, but pays off
in the long run, since you have less problems. And all these ugly
poles and transformers will vanish.



I'd love to have 3 phase, I've never seen it in a residence though, and
residential equipment is all single phase anyway, it works.

I kinda like above ground power, at least for the big stuff. Most of the
houses around here from the late 70s on have underground power, but some of
the old lines are starting to deteriorate so they've had to dig up streets
and flower beds to replace them.

"James Sweet" wrote in message
news:ZQawi.3100$hK5.368@trndny02...


Ugh. Putting them up for each individual hous is a very, very
historic way to do it.


I don't think there's one by every house, seems like you see them
every few poles.


Generally it's 4-10 houses per transformer, it's nice, it makes it
possible to have quite good voltage regulation. I rarely see mine change
by more than a volt plus or minus.


The right way to do this is to use bigger transformesr for 10-100 houese
and to bury 3-phase AC lines. A lot more expensive, but pays off
in the long run, since you have less problems. And all these ugly
poles and transformers will vanish.



I'd love to have 3 phase, I've never seen it in a residence though, and
residential equipment is all single phase anyway, it works.

I kinda like above ground power, at least for the big stuff. Most of the
houses around here from the late 70s on have underground power, but some
of the old lines are starting to deteriorate so they've had to dig up
streets and flower beds to replace them.


Isn't the 'high' voltage that you have in the US for powering washing
machines and the like, phase to phase ? Seems like it wouldn't be that hard
for the power company to put in the third phase as well ? (I might be
totally adrift on this one - I'm not a power engineer ;-) )

Arfa

"William Sommerwerck" wrote in message
...
So are you saying that a meter that measures *true* RMS
anything -- power, current, volts -- will do so correctly even
if the waveform is asymmetric about the zero point? I always
believed that an even distribution about the zero point was a
requirement for an accurate representation of an RMS value.

The RMS value of a waveform has nothing to do with the shape or symmetry
of
the waveform.

Assuming the meter is correctly designed, yes. RMS has a clear, specific
definition, and if the measurement is correctly implemented, the reading
will be correct.

Two qualifications... If the waveform is non-periodic, the measured RMS
value will vary according to the sample period. Also, if the waveform
includes a DC component, and the meter blocks it with a capacitor, then
the
RMS reading will not include the DC component.


Ah, OK. Perhaps it's non-periodicity that I'm getting confused with. As I
say, college seems a long-haired good music time ago now ...

Arfa

On Aug 12, 10:24 pm, "James Sweet" wrote:


Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
are so popular, though I still prefer a good CRT as it looks slightly better
to my eyes.


I don't like the way LCD/flat panel monitors look. The image isn't as
sharp and loses brightness unless you're sitting dead-center in front
of them, even the models that supposedly have a wider viewing angle.

In comp.sys.ibm.pc.hardware.misc James Sweet wrote:


EE friend of mine compared one to a $2500 power analyzer at work, found
that
the Kill A Watt performance is pretty much inline with the specs printed
for
it. It's not as good as the professional equipment, but it's really very
impressive for what it is and certainly adequate for consumer use. The
wonders of modern microelectronics, it's amazing what they can do with
one
inexpensive chip and a handfull of passive components. I still remember
when
a pocket calculator was $300, then a few years later $50 would buy one
just
as effective, and not long after that they were under $20 and those are
all
more capable than large machines costing many thousands just a few
decades
earlier.

Hmm. Interesting. I trust he did this right and tested non-ohmic
loads such as a PC PSU as well?



Yes, of course, pure resistive loads can be measured just fine with a
multimeter. We were interested primarily in using it to measure discharge
lamp systems in which the power factor and current waveforms can be all over
the place and vary greatly with the state and condition of the lamp. If the
meter wasn't able to handle odd waveforms, the power factor measurement
function would be useless, but it works pretty well, accuracy is within
about 2% on the sample tested.



Good to know, so it _can_ be done relatively cheaply today.

Arno

"James Sweet" wrote in message
news:ZQawi.3100$hK5.368@trndny02

I'd love to have 3 phase, I've never seen it in a
residence though, and residential equipment is all single
phase anyway, it works.

The German town I lived in during the late 70s had something like 440/3
phase which was used for the water heater. Obviously, it would work wonders
with motors.

As you no doubt know synchronous motors are the big thrill for 3 phase.

We seem to be making an end run on the issue by running DC motors through
transformerless AC-powered intelligent controllers.

I kinda like above ground power, at least for the big
stuff.

Interesting, because a lot of big stuff around here is underground until it
hits the neighborhood pole transformers. IOW, the next regional substation
up has all its ins and outs underground. Underground lines run to the
neighborhoods. They feed strings of poles in people's back yards.

Some people such as myself have converted their house feed to underground,
but it is pretty rare around here.

My application is peculiar - I live on a corner lot with a very narrow back
yard and lotsa trees. Also, my previouis above-ground drop was never code
and eventually failed. The part of the house where the power entry was no
longer exists.

Above-ground feed to the house was ugly no matter how it was done. The
utility's pricing scheme made the conversion to underground very
economically attractive, because my house needed a minimal length feed.
Their marketing people made up a price list with minimal initial costs and
buried most people's installation fees in the per-foot charge. I got quite
a bit of hardware and labor for my $250.

I hear that some utilities will convert people for free in some
neighborhoods.

Most of the houses around here from the late 70s
on have underground power, but some of the old lines are
starting to deteriorate so they've had to dig up streets
and flower beds to replace them.

Our neighborhood was built up from 1930 to 1955, so everything is above
ground. I've seen individual home conversions, but nothing on a neighborhood
scale.

"Richard Crowley" wrote in message

"Arny Krueger" wrote ...

You're aware that capacitive voltage dividers have flat
frequency response, right?

Perhaps you are not aware that many inexpensive consumer
mains power supplies use a capacitor rather than a
resistor as the series element of a shunt-regulated power supply.

Right, but that's not a true capacitive voltage divider.

The circuit is essentially a high-pass circuit and very
much has a rising response.

Those half-breed RC voltage dividers do need to be engineered carefully.

"Arno Wagner" wrote in message


In comp.sys.ibm.pc.hardware.misc Doc
wrote:

Recently I asked about suggestions regarding a UPS. I
ended up getting an 875 VA 525 Watt "Geek Squad" model
from Best Buy - yeah, yeah, everyone says Geek Squad
stuff is overhyped junk, but at $69 on sale, the price
seemed right.

Seems like it is discontinued - not on their current store list.

The price is all wrong.

(1) Made in China, sold in the US
(2) House brand
(3) Close out

Nobody can build a decent product
with these specs for that price.

Best Buy is actually the high priced spread, compared to some of their
competition.

You cannot even buy the
components needed in decent quality for that price.

But that is unit one up individual component pricing which has a lot of
overhead in it.

"Doc" wrote in message
oups.com
On Aug 12, 10:24 pm, "James Sweet"
wrote:


Yeah CRT monitors take a lot of juice, it's one of the
reasons flat panels are so popular, though I still
prefer a good CRT as it looks slightly better to my eyes.


I don't like the way LCD/flat panel monitors look. The
image isn't as sharp and loses brightness unless you're
sitting dead-center in front of them, even the models
that supposedly have a wider viewing angle.

Spend more money or wait 3 years! ;-)

In article Ju7wi.3782$r14.794@trndny06,
James Sweet wrote:

It does not extend the life. Back in the seventies when NiCd packs had
memory effect, folks were recommending deep discharge. But today, you
are more likely to wreck a NiCd pack by reverse-charging a cell that way.

I read recently that the memory effect "myth" was created due to cheap
chargers overcharging the batteries unless they were first fully discharged.
A decent intelligent charger should prevent this, and batteries have in
theory improved as well.

No, there actually _was_ memory effect at one time, and the Gates Battery
Handbook used to have a discussion about the chemistry involved. The
problem was solved some time in the late 1970s, but the notion on the part
of the users remained. And plenty of users since have destroyed perfectly
good battery packs by deep-discharging them and wrecking the weaker cells in
the pack, in order to avert a failure mode that hadn't existed for years.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Arfa Daily wrote:

I'd love to have 3 phase, I've never seen it in a residence though, and
residential equipment is all single phase anyway, it works.

I kinda like above ground power, at least for the big stuff. Most of the
houses around here from the late 70s on have underground power, but some
of the old lines are starting to deteriorate so they've had to dig up
streets and flower beds to replace them.


Isn't the 'high' voltage that you have in the US for powering washing
machines and the like, phase to phase ? Seems like it wouldn't be that hard
for the power company to put in the third phase as well ? (I might be
totally adrift on this one - I'm not a power engineer ;-) )

In the US, the high voltage distribution is done with three phases, shifted
120' from one another. You can also in many places order low voltage lines
with three-phase power, but it's not common in residential areas.

In most residential areas, they will send one leg of that three phase 3KV out
to a distribution transformer near your house. The secondary of that
transformer has a center-tap tied to the neutral, and then two hot wires
that are 180' out of phase. So neutral to one leg is 120V, but leg to leg
is 240V.

But this does not help you if you want to run a 25-foot turret lathe in
your garage, which requires three phases with a 120' shift between them.
For that, you either have to move to an industrial neighborhood, or call
the power company to pull three-phase 3KV in and then drop it down to
a low voltage with your own set of transformers. They will charge for this.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In comp.sys.ibm.pc.hardware.misc Scott Dorsey wrote:
Arfa Daily wrote:

I'd love to have 3 phase, I've never seen it in a residence though, and
residential equipment is all single phase anyway, it works.

I kinda like above ground power, at least for the big stuff. Most of the
houses around here from the late 70s on have underground power, but some
of the old lines are starting to deteriorate so they've had to dig up
streets and flower beds to replace them.


Isn't the 'high' voltage that you have in the US for powering washing
machines and the like, phase to phase ? Seems like it wouldn't be that hard
for the power company to put in the third phase as well ? (I might be
totally adrift on this one - I'm not a power engineer ;-) )

In the US, the high voltage distribution is done with three phases, shifted
120' from one another. You can also in many places order low voltage lines
with three-phase power, but it's not common in residential areas.

In most residential areas, they will send one leg of that three
phase 3KV out to a distribution transformer near your house. The
secondary of that transformer has a center-tap tied to the neutral,
and then two hot wires that are 180' out of phase. So neutral to
one leg is 120V, but leg to leg is 240V.

That would be 210V leg-to leg, because of the phase shift.

But this does not help you if you want to run a 25-foot turret lathe
in your garage, which requires three phases with a 120' shift
between them. For that, you either have to move to an industrial
neighborhood, or call the power company to pull three-phase 3KV in
and then drop it down to a low voltage with your own set of
transformers. They will charge for this.

Hmm. The typical approch in Europe is 15kV to large transformers
and then 3 phase distribution to the houses. Above ground is for
is moslty for rural areas, you do not see above ground lines in
cities, at least not in Germany or Switzerland. So getting three
phase is trivial. Typically flats have 3-phase times 16A (at 240V)
for electric stoves. Getting 3x25A at 240V is just some in-house
wiring. If you want 3x40A, you may need to have your feed checked,
since it is typically rated at 3x63A or 3x100A for larger houses.

Arno

In comp.sys.ibm.pc.hardware.misc Arny Krueger wrote:
"Doc" wrote in message
oups.com
On Aug 12, 10:24 pm, "James Sweet"
wrote:


Yeah CRT monitors take a lot of juice, it's one of the
reasons flat panels are so popular, though I still
prefer a good CRT as it looks slightly better to my eyes.


I don't like the way LCD/flat panel monitors look. The
image isn't as sharp and loses brightness unless you're
sitting dead-center in front of them, even the models
that supposedly have a wider viewing angle.

Spend more money or wait 3 years! ;-)

If you select your LCD carefully, you can get really good ones
for very reasonable prices. I have a Benq FP73G, which initially
anoyed me a bit with the vertical brightness dependency on viewing
angle. Now I do not notice it anymore. It is sharper than CRT by
at least one order of magintude. Of course you have to run at
native resolution. As with brighness, I found that I needed to
tweak gamma in some games. apart from that, no problems.

Arno

"Doc" wrote in message
oups.com...
I don't like the way LCD/flat panel monitors look. The image isn't as
sharp and loses brightness unless you're sitting dead-center in front
of them, even the models that supposedly have a wider viewing angle.

Then you should buy a decent flat panel. I went from an IIyama 22" CRT to an
IIyama 20" LCD and it is razorsharp compared to the CRT. And regarding
viewing angle: even watching from aside (175 deg.) it still looks like
watching a picture on a piece of paper.

Meindert

Arno Wagner wrote:

In most residential areas, they will send one leg of that three
phase 3KV out to a distribution transformer near your house. The
secondary of that transformer has a center-tap tied to the neutral,
and then two hot wires that are 180' out of phase. So neutral to
one leg is 120V, but leg to leg is 240V.

That would be 210V leg-to leg, because of the phase shift.

No, it's 180' phase shift. The two legs are directly out of phase,
therefore they sum. It's not three-phase, it's what they call
single-phase (even though it's really two phases).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"James Sweet" wrote ...
"Richard Crowley" wrote ...
Agree completely. They are great when used with the regular
sine-wave mains power grid. However note that many have
been fried beyond repair when used with any kind of square-
wave source: inverter, UPS, etc. even "stepped sine" waveforms.

The problem appears to be the capacitive voltage divider used
to power the Kill-A-Watt electronics. The high frequency harmonics
deliver way too much power to the shunt regulator through the
capacitor and something fries.


Interesting, well mine is the 240V UK version which I got back before I
found them offered here but from looking at the buttons and display it's
obviously the same unit as the Kill A Watt. At any rate I've tested it and
it works well all the way down to 60VAC, and frequencies from 30 Hz all
the way up to nearly 400Hz where the readings start to get screwy. I've
run it off inverters, used an adapter to hook it up to my 240V central
heat pump to measure that, it's taken everything I've tossed at it and so
far keeps working.

There are rumors that the manufacturer re-designed the
circuit to eliminate this flaw. It may not be a problem with
newer models(?)

The original problem was featured in a 2-page article in the
ham-radio magazine "QST".

"Arny Krueger" wrote ...
"Richard Crowley" wrote
"Arny Krueger" wrote ...

You're aware that capacitive voltage dividers have flat
frequency response, right?

Perhaps you are not aware that many inexpensive consumer
mains power supplies use a capacitor rather than a
resistor as the series element of a shunt-regulated power supply.

Right, but that's not a true capacitive voltage divider.

You are correct. I mis-characterized it as a "capacitive divider"
when only the series element was capacitive.

The circuit is essentially a high-pass circuit and very
much has a rising response.

Those half-breed RC voltage dividers do need to be engineered carefully.

Rumor is that the manufacturer re-designed the circuit to
eliminate the problem.

No, it's 180' phase shift. The two legs are directly out of phase,
therefore they sum. It's not three-phase, it's what they call
single-phase (even though it's really two phases).
--scott

In common parlance it's known as "split phase", which is not technically
correct. Proper description of this is "3-wire, single-phase, mid-point
neutral system".

Sparky

"Doc" wrote in message
oups.com

The transformer - if that's the correct term for it - big
gray basically cylindrical unit on top of a power pole -
near my house blew once. Powerful **BOOM** and a huge
column of flame.

Been there, seen that, from a few blocks away. The boom was audible and the
fire was visible from that distance.

The old transformer in my back yard smoked for several hours, but neither
exploded nor emitted flames. The replacements were appreciably larger!

Not sure what the fuel for the flame
was, do they have oil in them?

Yes, most pole transformers are filled with some kind of insulating,
heat-transferring oily liquid. It may contain nifty stuff like PCBs, though
hopefully those have all been removed.

Also a bit disconcerting
since anyone nearby surely would have been in jeopardy
from flaming debris.

There's a reason why they don't put these things in people's houses!

In fact oil-filled transformers are commonly put in dedicated rooms in
commercial buildings, but they have appropriate design and safety features.

Needless to say, power was out for a while on that one.

We had a transformer blow in a local substation, and had rotating blackouts
for about a week. It was about the size of a small house, and the
replacement had to be trucked in from out of state.

On Mon, 13 Aug 2007 20:53:00 -0700, Doc
wrote:

On Aug 13, 12:32 pm, kony wrote:

The price is all wrong. Nobody can build a decent product with
these specs for that price. You cannot even buy the components
needed in decent quality for that price.

Depending on your definition of "decent", this may be true,
but it's going to be roughly equivalent to what you'd buy
from APC as a 500VA for about $50 so if that's what the
budget allows, it's not an exceptionally low price (also
considering you can sometimes get the APC discounted or with
rebate putting it closer to $20-30 than to $50.


FWIW, I was in that same Best Buy today and the UPS model I got for
$69 was back to its normal price of $119.


I should elaborate that roughly equivalent did not mean same
thing just spec'd less conservatively, did not mean to
include current capability and/or battery size, rather these
parameters were probably increased correspondingly.

On Tue, 14 Aug 2007 08:58:08 -0400, "Arny Krueger"
wrote:


You cannot even buy the
components needed in decent quality for that price.

But that is unit one up individual component pricing which has a lot of
overhead in it.

Quite true, practically anything electronic is this way.
Ironically even an empty project case can cost more than
some junk from China which is a complete product inside a
custom case.

On Tue, 14 Aug 2007 05:03:15 -0700, Doc
wrote:

On Aug 12, 10:24 pm, "James Sweet" wrote:


Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
are so popular, though I still prefer a good CRT as it looks slightly better
to my eyes.


I don't like the way LCD/flat panel monitors look. The image isn't as
sharp

I'd have to disagree on this, if there is anything that is a
clear win for LCD, it is image sharpness... it doesn't get
any sharper than having individual pixel representation.
This can be offset in perception if the particular LCD has
poor contrast but it is still just as "sharp", though not as
vibrant.


and loses brightness unless you're sitting dead-center in front
of them, even the models that supposedly have a wider viewing angle.

True but it's a computer monitor, how many positions do you
really need to be in while viewing it?

"Arfa Daily" writes:



OK. I'm not sure that 'RMS' is the right term to attach to any value derived
from a ragged-arsed waveform, as it is a mathematical function normally
associated with symetrical waveforms, which the draw by a SMPS may very well
not be, but I see what you're saying.

It's defined as heating value. Some RMS meters were in fact calorimeters.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:
"Arfa Daily" writes:

OK. I'm not sure that 'RMS' is the right term to attach to any value derived
from a ragged-arsed waveform, as it is a mathematical function normally
associated with symetrical waveforms, which the draw by a SMPS may very well
not be, but I see what you're saying.

It's defined as heating value. Some RMS meters were in fact calorimeters.

Bird still makes a couple models that are. Necessary as primary standards.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 8/14/2007, Arfa Daily posted this:
"William Sommerwerck" wrote in message
...
So are you saying that a meter that measures *true* RMS
anything -- power, current, volts -- will do so correctly even
if the waveform is asymmetric about the zero point? I always
believed that an even distribution about the zero point was a
requirement for an accurate representation of an RMS value.

The RMS value of a waveform has nothing to do with the shape or symmetry of
the waveform.

Assuming the meter is correctly designed, yes. RMS has a clear, specific
definition, and if the measurement is correctly implemented, the reading
will be correct.

Two qualifications... If the waveform is non-periodic, the measured RMS
value will vary according to the sample period. Also, if the waveform
includes a DC component, and the meter blocks it with a capacitor, then the
RMS reading will not include the DC component.


Ah, OK. Perhaps it's non-periodicity that I'm getting confused with. As I
say, college seems a long-haired good music time ago now ...

Arfa

I agree with William Sommerwerck's more thorough analysis; the DC
problem (which I hadn't thought of) is pretty interesting too :-).

I agree about the confusion you mention - it makes sense; BTW, the way
around it is to use long sampling times, as I said in my post, although
I didn't go that one step further: to think about non-periodicity - &
understand it :-)

BTW, some true RMS meters use an entirely different approach[1]: they
measure the temperature of a resistor which is heated by the current
flowing through it when it is shunted across the line. This is (1)
potentially pretty accurate, and (2) probably very very slow to respond
to changes - i.e, an implied long sampling interval :-)

I guess we're OT here, but I admit that I'm having fun...

[1] Well, I'm not sure why I said 'different' - we haven't discussed
the method used, have we?

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

On 8/14/2007, kony posted this:
On Tue, 14 Aug 2007 05:03:15 -0700, Doc
wrote:

On Aug 12, 10:24 pm, "James Sweet" wrote:


Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
are so popular, though I still prefer a good CRT as it looks slightly
better to my eyes.


I don't like the way LCD/flat panel monitors look. The image isn't as
sharp

I'd have to disagree on this, if there is anything that is a
clear win for LCD, it is image sharpness... it doesn't get
any sharper than having individual pixel representation.
This can be offset in perception if the particular LCD has
poor contrast but it is still just as "sharp", though not as
vibrant.

I wonder if Doc is running his LCD at a non-native resolution...

and loses brightness unless you're sitting dead-center in front
of them, even the models that supposedly have a wider viewing angle.

True but it's a computer monitor, how many positions do you
really need to be in while viewing it?

:-)

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

On 8/14/2007, Gene E. Bloch posted this:
On 8/14/2007, Arfa Daily posted this:
"William Sommerwerck" wrote in message
...
So are you saying that a meter that measures *true* RMS
anything -- power, current, volts -- will do so correctly even
if the waveform is asymmetric about the zero point? I always
believed that an even distribution about the zero point was a
requirement for an accurate representation of an RMS value.

The RMS value of a waveform has nothing to do with the shape or symmetry
of
the waveform.

Assuming the meter is correctly designed, yes. RMS has a clear, specific
definition, and if the measurement is correctly implemented, the reading
will be correct.

Two qualifications... If the waveform is non-periodic, the measured RMS
value will vary according to the sample period. Also, if the waveform
includes a DC component, and the meter blocks it with a capacitor, then
the
RMS reading will not include the DC component.


Ah, OK. Perhaps it's non-periodicity that I'm getting confused with. As I
say, college seems a long-haired good music time ago now ...

Arfa

I agree with William Sommerwerck's more thorough analysis; the DC problem
(which I hadn't thought of) is pretty interesting too :-).

I agree about the confusion you mention - it makes sense; BTW, the way around
it is to use long sampling times, as I said in my post, although I didn't go
that one step further: to think about non-periodicity - & understand it :-)

BTW, some true RMS meters use an entirely different approach[1]: they measure
the temperature of a resistor which is heated by the current flowing through
it when it is shunted across the line. This is (1) potentially pretty
accurate, and (2) probably very very slow to respond to changes - i.e, an
implied long sampling interval :-)

I guess we're OT here, but I admit that I'm having fun...

[1] Well, I'm not sure why I said 'different' - we haven't discussed the
method used, have we?

I spoke just a bit too soon - the calorimetric method was mentioned in
some recent posts in this thread that I just saw.

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

"Arny Krueger" wrote in message
. ..
"Doc" wrote in message
oups.com

The transformer - if that's the correct term for it - big
gray basically cylindrical unit on top of a power pole -
near my house blew once. Powerful **BOOM** and a huge
column of flame.

Been there, seen that, from a few blocks away. The boom was audible and
the fire was visible from that distance.

The old transformer in my back yard smoked for several hours, but neither
exploded nor emitted flames. The replacements were appreciably larger!

Not sure what the fuel for the flame
was, do they have oil in them?

Yes, most pole transformers are filled with some kind of insulating,
heat-transferring oily liquid. It may contain nifty stuff like PCBs,
though hopefully those have all been removed.

Also a bit disconcerting
since anyone nearby surely would have been in jeopardy
from flaming debris.

There's a reason why they don't put these things in people's houses!

In fact oil-filled transformers are commonly put in dedicated rooms in
commercial buildings, but they have appropriate design and safety
features.

Needless to say, power was out for a while on that one.

We had a transformer blow in a local substation, and had rotating
blackouts for about a week. It was about the size of a small house, and
the replacement had to be trucked in from out of state.

Many years ago, I was hanging out of the bedroom window at 2am, watching a
spectacular thunderstorm that had been raging, and circling round my
location, for an hour or so. About 200yds up the road, where it ran out to a
dirt track, and no houses were yet built, was a pole, with a tranny on it
that I would guess to have been perhaps 3ft x 2ft x 2ft. It fed just the
farm in the field behind my house.

I was looking straight up the road, when the pole took what looked like a
direct hit. It probably actually wasn't direct, as I guess that would have
just vapourised the whole thing, but close enough anyway, that there was no
discernible delay between the stroke flash, and the bang, which was so loud
that I thought the vibration was going to bring the house down around me.
Anyway, as I continued to watch, half blinded, an orange glow like a plasma
ball started to grow around the top of the pole. It expanded out until it
looked the size of a small weather balloon, then just hung there for several
seconds. Then, without warning, the top of the pole - presumably the
transformer - just exploded with a huge bang, a sheet of flame, and a shower
of sparks. The orange ball was immediately dissipated. When I was able to
look again, the top of the pole was on fire. The whole street was without
power for 3 days.

When I went to look at the pole the next morning, there was just a charred
stump at the top. What was left of the tranny was on the ground, and of
course, the lines were down, but oddly intact, as they hung on the next pole
out across the field. The tranny was three phase 11kv to 240v I think. Three
lines plus one across the top, anyway. I don't know how much of this
pyrotechnic display was as a result of the 11kv, or of megavolts getting in
there from the lightning strike, but whichever, it was one of the most
spectacular things that I've ever seen.

I now live in a house further up the same road, and the pole and tranny were
moved from the roadside to the bottom of my neighbour's garden. A couple of
years back, the electricity company put in a new underground feed to the
farm, and came and took the overhead down. My neighbour asked them to leave
the pole, as he has a rather nice Russian Ivy growing up it, that is like a
huge bush, or tree even. Curiously, when the tranny was in place, the ivy
never grew closer than a foot or so to the platform where it was mounted.
Since it's gone, the ivy now grows right to the top, so obviously, plants
can sense the field around the high voltage components, and don't like it.
Makes you wonder whether there's anything in these claims that high voltage
overheads cause cancer in kids ...

Arfa

"CBFalconer" wrote in message
...
Arfa Daily wrote:

... snip ...

OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.

Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.


Explain ?

Arfa

"kony" wrote in message
...
On Tue, 14 Aug 2007 05:03:15 -0700, Doc
wrote:

On Aug 12, 10:24 pm, "James Sweet" wrote:


Yeah CRT monitors take a lot of juice, it's one of the reasons flat
panels
are so popular, though I still prefer a good CRT as it looks slightly
better
to my eyes.


I don't like the way LCD/flat panel monitors look. The image isn't as
sharp

I'd have to disagree on this, if there is anything that is a
clear win for LCD, it is image sharpness... it doesn't get
any sharper than having individual pixel representation.

snip

Agreed, but only if in native resolution, as others have said, and only if
what you are viewing is standing still. Even with the fastest LCD panels,
motion blur is still a problem, although probably more noticable at the
lower resolutions offered by 'standard' TV transmissions displayed on
standard LCD TV sets. Much as I like the picture on my (expensive)
widescreen HP LCD monitor, and given that I do agree with you about
sharpness, I still have to come down just on James' side in that I too think
that there is something fundamentally 'better' looking about a good fine
dot-pitch CRT monitor, but if you asked me to define "good" in this context,
I don't think that I could ...

Arfa

Arfa Daily wrote:
"CBFalconer" wrote in message
Arfa Daily wrote:

... snip ...

OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.

Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.

Explain ?

The integral is peak voltage times current. Simple. Not 0.7 *
peak voltage. Current is also constant for resistive loads, not
proportional to voltage. RMS doesn't work.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
http://cbfalconer.home.att.net



--
Posted via a free Usenet account from http://www.teranews.com

On 8/14/2007, Arfa Daily posted this:
"CBFalconer" wrote in message
...
Arfa Daily wrote:

... snip ...

OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.

Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.


Explain ?

Arfa

My interpretation: you seem to be saying that some meters produce an
RMS value by applying a simple factor to the peak value of the voltage,
and you seem to be saying that it works for any symmetrical wave form.
For a sine wave, as I mentioned elsewhere in this thread, this factor
would be (root 2)/2. CBFalconer mentioned a square wave as a
counter-example. Square waves are obviously quite symmetrical, but for
them, the magic factor is 1, assuming a perfect square wave. There's no
such thing, of course, but the factor is still pretty close to 1.

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

In comp.sys.ibm.pc.hardware.misc Scott Dorsey wrote:
Arno Wagner wrote:

In most residential areas, they will send one leg of that three
phase 3KV out to a distribution transformer near your house. The
secondary of that transformer has a center-tap tied to the neutral,
and then two hot wires that are 180' out of phase. So neutral to
one leg is 120V, but leg to leg is 240V.

That would be 210V leg-to leg, because of the phase shift.

No, it's 180' phase shift. The two legs are directly out of phase,
therefore they sum. It's not three-phase, it's what they call
single-phase (even though it's really two phases).
--scott

You are right. Somehow I read 120' there.

Arno

On Wed, 15 Aug 2007 00:59:34 GMT, "Arfa Daily"
wrote:

Agreed, but only if in native resolution, as others have said, and only if
what you are viewing is standing still. Even with the fastest LCD panels,
motion blur is still a problem, although probably more noticable at the
lower resolutions offered by 'standard' TV transmissions displayed on
standard LCD TV sets.

Have you seen significant motion blur on a current
generation smaller LCD? It seems everyone is upsizing which
offsets the improvements being made.

Isn't the 'high' voltage that you have in the US for powering washing
machines and the like, phase to phase ? Seems like it wouldn't be that
hard for the power company to put in the third phase as well ? (I might be
totally adrift on this one - I'm not a power engineer ;-) )



It's a center tapped 240V transformer that feeds houses, washing machines
are 120V, but large loads like dryers, cook stoves, central AC, etc will
wire from hot to hot with a double pole breaker to get 240V, it's still
single phase.

"CBFalconer" wrote in message
...
Arfa Daily wrote:
"CBFalconer" wrote in message
Arfa Daily wrote:

... snip ...

OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.

Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.

Explain ?

The integral is peak voltage times current. Simple. Not 0.7 *
peak voltage. Current is also constant for resistive loads, not
proportional to voltage. RMS doesn't work.


OK. Well in that case, I don't think that I was over-simplifying, because if
you have read the whole thread, you will see that it was I who questioned
the validity of attaching an RMS value to a non-sinusoidal waveform.
However, several posters then came back to me with considerable levels of
mathematical proof, to say that RMS was a valid notion for any waveshape or
symmetry factor, the only qualifiers being DC content or variable cycle
periodicity. Although it might not be too clear, that second paragraph was
more of a musing based on that. My original contention was that a power
meter (or whatever) designed to derive and display an RMS value from a sine
wave, would not give a meaningful reading from non-sinusoidal or
non-symmetrical drawing loads, such as a SMPS may be, for instance. The
replies suggested that the waveshape was immaterial, and that the chipset
could very easily still calculate a meaningful result. I was a little
sceptical about this, as it seemed to fly in the face of what I was taught
many years ago in college, but I bowed to what seemed to be superior
knowledge in the field.

Now, you seem to be saying something quite different ? Comments ?

Arfa

"kony" wrote in message
...
On Wed, 15 Aug 2007 00:59:34 GMT, "Arfa Daily"
wrote:

Agreed, but only if in native resolution, as others have said, and only if
what you are viewing is standing still. Even with the fastest LCD panels,
motion blur is still a problem, although probably more noticable at the
lower resolutions offered by 'standard' TV transmissions displayed on
standard LCD TV sets.

Have you seen significant motion blur on a current
generation smaller LCD? It seems everyone is upsizing which
offsets the improvements being made.

Well, certainly on LCD TV sets, yes. Oddly enough, I was looking at just
that in a store last night. They all had a studio-based news broadcast on
them, and it was superb as long as they were in the studio, where everything
was basically standing still, and properly lit. As soon as it cut to an OB
on the other hand, there was motion blur on them ALL. Some were worse than
others in that the blur was not just a function of panel speed, but also
drive artifacts. These were not cheap sets either. Many were from big name
houses. The larger screen sets actually seemed to fare somewhat better than
the small ones in my opinion, and the plasmas were a little better again,
but none of them produced what I would describe as a 'good' picture in this
respect, compared to a CRT set of any size or vintage - even my 10 year old
large screen Toshiba. There's a world of difference between LCD pixel
switching times in the mS bracket, and fast phosphor reponses down in the uS
range.

I actually think that at the moment, digital display technology - without
wishing to open up *that* can of worms again - lags behind CRT display
technology, by a significant amount. Next time you go to the cinema, look up
at the booth window and see if you can see film looping around the ceiling.
If you can't, then it uses one of those new-fangled DLP video projectors.
Sit back comfortably with your popcorn, and wonder what's happened to your
eyes, when the first car drives across the screen ... d;~}

Arfa

Arfa Daily wrote:
"CBFalconer" wrote in message
...
Arfa Daily wrote:
"CBFalconer" wrote in message
Arfa Daily wrote:
... snip ...
OK. I'm not sure that 'RMS' is the right term to attach to any
value derived from a ragged-arsed waveform, as it is a mathematical
function normally associated with symetrical waveforms, which the
draw by a SMPS may very well not be, but I see what you're saying.

What I am trying to say is that a chip which is designed to produce
an RMS reading from a sine wave, may well produce a meaningful
figure from a non-sinusoidal waveform also, but *only* if it is
still symetrical.
Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.
Explain ?
The integral is peak voltage times current. Simple. Not 0.7 *
peak voltage. Current is also constant for resistive loads, not
proportional to voltage. RMS doesn't work.


OK. Well in that case, I don't think that I was over-simplifying, because if
you have read the whole thread, you will see that it was I who questioned
the validity of attaching an RMS value to a non-sinusoidal waveform.
However, several posters then came back to me with considerable levels of
mathematical proof, to say that RMS was a valid notion for any waveshape or
symmetry factor, the only qualifiers being DC content or variable cycle
periodicity. Although it might not be too clear, that second paragraph was
more of a musing based on that. My original contention was that a power
meter (or whatever) designed to derive and display an RMS value from a sine
wave, would not give a meaningful reading from non-sinusoidal or
non-symmetrical drawing loads, such as a SMPS may be, for instance. The
replies suggested that the waveshape was immaterial, and that the chipset
could very easily still calculate a meaningful result. I was a little
sceptical about this, as it seemed to fly in the face of what I was taught
many years ago in college, but I bowed to what seemed to be superior
knowledge in the field.

Now, you seem to be saying something quite different ? Comments ?

Arfa


Sorry to butt in here, but when I was studying such things, the RMS
value of a current or voltage waveform was calculated by working out the
area inside the curve plotted over a full cycle, which then allowed you
to calculate an equivalent DC value. This involved counting squares on
graph paper of the plotted waveform or similarly counting squares on a
calibrated oscilloscope tube face. The earlier & most of the current
cheap meters that give an alleged RMS reading take a peak reading &
apply a correction factor of 0.707 to it (1 divided by the (near enough)
square root of 2), as that gives the right answer with a clean sine
wave, which is what most of these meters are used to measure. (Mains
power round here is near enough a pure sine wave that you can ignore the
error, as it's less than the accuracy of the meter)
The RMS value of a (theoretical) pure square wave is exactly the same as
the average of the absolute values of the positive & negative peaks, as
the value is either fully positive or fully negative, with, in theory,
no other value being present.

The most (theoretically) accurate way to measure RMS values is to use a
hot wire meter, which doesn't care what the waveform is, it just
measures the heating effect which is more or less frequency independent
& includes any DC offset automatically.


Tciao for Now!

John.