Dan Musicant wrote:
On Sat, 24 Oct 2009 23:16:31 -0500, zxcvbob 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
ortable 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

Your "accurate" system measures VA, not Watts. Read up on power factor,
the effect of an out-of-phase relationship between volts and amps.

In article , Tony wrote:
dpb wrote:
Tony wrote:
...
... As far as electronics, about the worst thing you can do is turn it
off and on again while it's hot. ...

Where did you get this gem from?

Electronics training and real life experience. It's quite simple
actually, most people know that most electronic failures occur during
the power up surge. That power up surge is even more detrimental when
the components are hot.

I have two problems with this:

1. I have a lot of experience with power-cycle-when-hot on consumer
electronics, not accounting for any failures except for two cases
where the unit was previously showing bad signs related to how it ages
when operating hot. One of them was an integral-electronic-ballast CFL,
the other was a computer monitor.

I have had a few failures in homebrew electronics from
power-cycle-when-hot, always in circuits-under-development that were also
at that time prone to failing at power-on-when-cold and also during steady
operation. Most of those were with a homebrew solid state Tesla coil,
some with a homebrew electronic ballast for metal halide lamps.

2. The first half second of operation does not produce significant
heating of components other than the power rectifier and the filter
capacitor after the power rectifier, maybe slightly also in a following
voltage regulator. My experiece with these components failing is that
most failures here are from capacitors gradualy going bad and failing
during steady operation, less often rectifiers failing during steady
operation.

Voltage withstanding capacity of stressed failure-prone components
generally does not worsen with increasing temperature. One exception is
bipolar transistors, and even then not voltage alone - but from a
combination of voltage, power dissipation and temperature. Power-cycling
while hot gives them the extra stress only while signal is present and if
the power supply is unregulated.

- Don )

In , D. Musicant wrote in part:

Depends how deep your pockets are. Some people don't give a damn about
20 watts. Others do. 20 watts costs me about $20/year when drawn
24/7/365. Personally, I want to know.

20 watts 24/7/365 costs me $26 per year, in the Pennsylvania
portion of the Philadelphia metro area. Chicago and NYC are similar.

Philadelphia regular residential rate has a surcharge for using more
than 500 KWH per month during air conditioning season - so an
eliminatable 20 watt continuous load may cost more like $30 annually.

There is a looming threat for this to increase substantially in 14
months, when a rate regulation affecting me ends. My power company is
advertizing this on radio, advising their customers to get into
conservation.

- Don Klipstein )

Here on Long Island that's $37 per year.

Bernie

"Don Klipstein" wrote in message
...
In , D. Musicant wrote in
part:

Depends how deep your pockets are. Some people don't give a damn about
20 watts. Others do. 20 watts costs me about $20/year when drawn
24/7/365. Personally, I want to know.

20 watts 24/7/365 costs me $26 per year, in the Pennsylvania
portion of the Philadelphia metro area. Chicago and NYC are similar.

Philadelphia regular residential rate has a surcharge for using more
than 500 KWH per month during air conditioning season - so an
eliminatable 20 watt continuous load may cost more like $30 annually.

There is a looming threat for this to increase substantially in 14
months, when a rate regulation affecting me ends. My power company is
advertizing this on radio, advising their customers to get into
conservation.

- Don Klipstein )

Don Klipstein wrote:
In article , Tony wrote:
dpb wrote:
Tony wrote:
...
... As far as electronics, about the worst thing you can do is turn it
off and on again while it's hot. ...
Where did you get this gem from?
Electronics training and real life experience. It's quite simple
actually, most people know that most electronic failures occur during
the power up surge. That power up surge is even more detrimental when
the components are hot.

I have two problems with this:
....[examples elided for brevity]...

My response was in response to work done for NRC some time ago in
classifying failures--no discernible trend of "hot power-on" failure was
observable. That was some time ago but I'm not aware of there being
failure data that corroborates that phenomenon particularly...

--

On Sun, 01 Nov 2009 15:28:15 -0600, cjt
wrote:

an Musicant wrote:
: On Sat, 24 Oct 2009 23:16:31 -0500, zxcvbob 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
: ortable 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
:
:Your "accurate" system measures VA, not Watts. Read up on power factor,
:the effect of an out-of-phase relationship between volts and amps.

Could you explain further? I'm measuring amps on 120v AC. My
understanding is AC amps x AC volts = Watts. Not so? Why?

Dan

PS What's VA?


Email: dmusicant at pacbell dot net

Dan Musicant wrote:
On Sun, 01 Nov 2009 15:28:15 -0600, cjt
wrote:

an Musicant wrote:
: On Sat, 24 Oct 2009 23:16:31 -0500, zxcvbob 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
: ortable 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
:
:Your "accurate" system measures VA, not Watts. Read up on power factor,
:the effect of an out-of-phase relationship between volts and amps.

Could you explain further? I'm measuring amps on 120v AC. My
understanding is AC amps x AC volts = Watts. Not so? Why?

Dan

PS What's VA?


Email: dmusicant at pacbell dot net

Amps times volts equal watts when the current and voltage are in
phase (i.e. a purely resistive load). When they are out of phase,
there's an additional "power factor" applied to convert what is
then volt-amps (VA) to watts (W). It all goes back to the true
definition of AC watts, which is an integral (as in calculus) over
time of instantaneous voltage times instantaneous current. If you
actually do the calculus, you should be able to determine power
factor as a function of phase angle. I bet the folks in Wikipedia
(or your favorite source on the Internet, whatever it might be)
have an even clearer explanation. :-)

Don Klipstein wrote:
In article , Tony wrote:
dpb wrote:
Tony wrote:
...
... As far as electronics, about the worst thing you can do is turn it
off and on again while it's hot. ...
Where did you get this gem from?
Electronics training and real life experience. It's quite simple
actually, most people know that most electronic failures occur during
the power up surge. That power up surge is even more detrimental when
the components are hot.

I have two problems with this:

1. I have a lot of experience with power-cycle-when-hot on consumer
electronics, not accounting for any failures except for two cases
where the unit was previously showing bad signs related to how it ages
when operating hot. One of them was an integral-electronic-ballast CFL,
the other was a computer monitor.

I have had a few failures in homebrew electronics from
power-cycle-when-hot, always in circuits-under-development that were also
at that time prone to failing at power-on-when-cold and also during steady
operation. Most of those were with a homebrew solid state Tesla coil,
some with a homebrew electronic ballast for metal halide lamps.

2. The first half second of operation does not produce significant
heating of components other than the power rectifier and the filter
capacitor after the power rectifier, maybe slightly also in a following
voltage regulator. My experiece with these components failing is that
most failures here are from capacitors gradualy going bad and failing
during steady operation, less often rectifiers failing during steady
operation.

Voltage withstanding capacity of stressed failure-prone components
generally does not worsen with increasing temperature. One exception is
bipolar transistors, and even then not voltage alone - but from a
combination of voltage, power dissipation and temperature. Power-cycling
while hot gives them the extra stress only while signal is present and if
the power supply is unregulated.

- Don )

I've never done any studies on it, so I suppose it's time to stop the
old wives tale I was taught in school dealing with power up failures.

As far as a hot power cycle, well I suppose the few times it happened to
me was just a coincidence. Again, maybe that's an old wives tale also?

dpb wrote:
Don Klipstein wrote:
In article , Tony wrote:
dpb wrote:
Tony wrote:
...
... As far as electronics, about the worst thing you can do is turn
it off and on again while it's hot. ...
Where did you get this gem from?
Electronics training and real life experience. It's quite simple
actually, most people know that most electronic failures occur during
the power up surge. That power up surge is even more detrimental
when the components are hot.

I have two problems with this:
...[examples elided for brevity]...

My response was in response to work done for NRC some time ago in
classifying failures--no discernible trend of "hot power-on" failure was
observable. That was some time ago but I'm not aware of there being
failure data that corroborates that phenomenon particularly...

Well I suppose I was taught wrong, wouldn't be the first time.