Re: CS>Current Measurement, Wheres the Logic ?
Wayne Fugitt wrote: Morning Marshall, Maybe you can tell me what I am missing or what I do not understand. The only reason one measures the current is that he wants to know the current flow in a specific circuit, A finite circuit at a specific time and condition. It may be a changing circuit, possibly a CS batch. If one starts adding components such as a resistor, no matter the size, he has changed the circuit, and the reading will be meaningless. It is not meaningless, and can usually be determined, but is often insignificant. For instance if one has a CS system which has a 10 K resistor in series with 30 volts to provide a 3 mA current limit, and you put a 1 ohm resistor in series to measure the current, it will drop no more than 3 mV. That is insignificant to the circuit, and the 10,001 ohms will be in error by 1/100 of what a 1% resistor tolerance is. The ratio of the change could be somewhat specific, but in most cases it will not be. ( actually unknown ) This would be determined by the ratio of the resistance added to the ratio of the original circuit. Once again, if you are using a sufficiently low value resistor, the difference is insignificant. Just because someone made a mistake and connected the meter wrong, is no need to think they could not still do it correctly. Well, first I am not sure she was connecting it wrong, since I am not sure what she was trying to accomplish. Was she trying to measure the short circuit current of the power supply? If so the connection was right, but the sequence of applying power, and/or selection of range was wrong. If she was wanting to measure the current through a CS cell, then the connection was wrong. But if connected right, could have the same effect, if the wires in the cell were accidentally shorted together unless she is using a limiting resistor. Using a small shunt resistor and the meter on volts is less likely to cause a failure in the meter than measuring mA current if something does go wrong. I hate to see people advising beginners with makeshift methods, half truths, and encouraging them to wish, hope and pray, and go around in circles. Then one year later, or two years later, they will still be confused and not understand 1 , 1, 1 One Volt, One Ohm, and One AMP. Lets see, what it V = I*R, I = V/R or R= V/I? Just kidding. If they cannot understand that, when it is explained, or study it a few minutes, then they should Abandon Ship, ASAP. The only reason I can see to use a known resistor with a current meter is to test the meter to see if it works. No, you use a known resistor with a voltage meter. Stay away from the current meter selection entirely, the voltage input is much more overload tolerant than the current input. Any one of us could make a simple drawing, or a picture or two showing how to connect a volt meter or a current meter. Likely 10,000 exist on the internet. Once when installing a production line automation system I built, one of my men connected a transformer backwards to 480 VAC. When he used the meter, it was destroyed, not beyond repair, but beyond recognition. He was lucky that he did not loose a finger or two, or more. Yep, I evaporated the entire shaft of a screwdriver once when I accidentally got it across the terminals of a car battery. For a while I thought I was going to be both blind AND deaf. My sight came back, but my ears still ring. We all know, the higher the voltage, the less forgiving it actually is, to equipment and to humans. Maybe I missed the whole point about using the resistor. Maybe. >> It is a somewhat derogatory term Some are transformers, putting out 24 or so volts AC, but most have a diode bridge in them and a filtering capacitor to supply DC. I think the term, "Wall Wart" means only one simple thing, The people who use it have not a clue what they actually have. If they did, they would use the proper term, Power supply or Transformer. Plain and simple. I use the term, and know darned well what they are, and what is in them. I tend to use the term because I think they are ugly, and that tends to convey that feeling. Using a term like power supply or transformer is no better, when I hear power supply, I think of either a bench supply, or one of the units that go into a computer. A transformer can be anything from a balm antenna transformer to an HO train set transformer, to a neon sign transformer to a huge one in a substation. Wall wart describes the physical appearance and approximate size, transformer or power supply describes the function. Neither alone really gives a complete description, one would need to say a wall wart power supply, or a wall wart rated at 24 VDC @ 500 mA for example. It is one or the other, not a stupid Wall Wart. I keep a precision 50 AMP meter shunt in my truck. I built it in a nice plastic box with terminal strips installed on the box. ( for DC ) I can measure 3 amp
Re: CS>Current Measurement, Wheres the Logic ?
http://en.wikipedia.org/wiki/Balun
A balun, pronounced /'bæl.ʊn/ ("bal-un"), is a passive
electronic device that converts between balanced and
unbalanced electrical signals. They often also change
impedance. Baluns can take many forms and their presence is
not always obvious. They always involve some form of
electromagnetic coupling.
Marshall Dudley wrote:
Wayne Fugitt wrote:
Morning Marshall,
Maybe you can tell me what I am missing or what I do not understand.
The only reason one measures the current is that he wants
to know the current flow in a specific circuit,
A finite circuit at a specific time and condition.
It may be a changing circuit, possibly a CS batch.
If one starts adding components such as a resistor, no matter the
size, he has changed the circuit, and the reading will be meaningless.
It is not meaningless, and can usually be determined, but is often
insignificant. For instance if one has a CS system which has a 10 K
resistor in series with 30 volts to provide a 3 mA current limit, and
you put a 1 ohm resistor in series to measure the current, it will drop
no more than 3 mV. That is insignificant to the circuit, and the 10,001
ohms will be in error by 1/100 of what a 1% resistor tolerance is.
The ratio of the change could be somewhat specific, but in most cases
it will not be. ( actually unknown )
This would be determined by the ratio of the resistance added to the
ratio of the original circuit.
Once again, if you are using a sufficiently low value resistor, the
difference is insignificant.
Just because someone made a mistake and connected the meter wrong, is
no need to think they could not still do it correctly.
Well, first I am not sure she was connecting it wrong, since I am not
sure what she was trying to accomplish. Was she trying to measure the
short circuit current of the power supply? If so the connection was
right, but the sequence of applying power, and/or selection of range was
wrong. If she was wanting to measure the current through a CS cell,
then the connection was wrong. But if connected right, could have the
same effect, if the wires in the cell were accidentally shorted together
unless she is using a limiting resistor. Using a small shunt resistor
and the meter on volts is less likely to cause a failure in the meter
than measuring mA current if something does go wrong.
I hate to see people advising beginners with makeshift methods, half
truths, and encouraging them to
wish, hope and pray, and go around in circles.
Then one year later, or two years later, they will still be confused
and not understand 1 , 1, 1
One Volt, One Ohm, and One AMP.
Lets see, what it V = I*R, I = V/R or R= V/I? Just kidding.
If they cannot understand that, when it is explained, or study it a
few minutes, then they should Abandon Ship, ASAP.
The only reason I can see to use a known resistor with a current meter
is to test the meter to see if it works.
No, you use a known resistor with a voltage meter. Stay away from the
current meter selection entirely, the voltage input is much more
overload tolerant than the current input.
Any one of us could make a simple drawing, or a picture or two showing
how to connect a volt meter or a current meter.
Likely 10,000 exist on the internet.
Once when installing a production line automation system I built, one
of my men connected a transformer backwards to
480 VAC. When he used the meter, it was destroyed, not beyond repair,
but beyond recognition. He was lucky that he did not loose a finger
or two, or more.
Yep, I evaporated the entire shaft of a screwdriver once when I
accidentally got it across the terminals of a car battery. For a while
I thought I was going to be both blind AND deaf. My sight came back,
but my ears still ring.
We all know, the higher the voltage, the less forgiving it actually
is, to equipment and to humans.
Maybe I missed the whole point about using the resistor.
Maybe.
>> It is a somewhat derogatory term
Some are transformers, putting out 24 or so volts AC, but most have a
diode bridge in them and a filtering capacitor to supply DC.
I think the term, "Wall Wart" means only one simple thing,
The people who use it have not a clue what they actually have. If
they did, they would use the proper term,
Power supply or Transformer. Plain and simple.
I use the term, and know darned well what they are, and what is in
them. I tend to use the term because I think they are ugly, and that
tends to convey that feeling. Using a term like power supply or
transformer is no better, when I hear power supply, I think of either a
bench supply, or one of the units that go into a computer. A transformer
can be anything from a balm antenna transformer to an HO train set
transformer, to a neon sign transformer to a huge one in a substation.
Wall wart describes the physical appearance and approximate size,
transformer or power supply describes the functi
Re: CS>Current Measurement, Wheres the Logic ?
Evening Marshall, >> At 01:24 PM 12/21/2007, you wrote: Thanks for all the details. It is not meaningless, and can usually be determined, resistor in series with 30 volts to provide a 3 mA current limit, and you put a 1 ohm resistor in series to measure the current, it will drop no more than 3 mV. Looks like you made a meter shunt. Of course I meant for the original task someone wanted to do. If they could not measure the CS batch current, ... likely they could not do much else, The statements you made are all technically correct and actually need no comment. Some don't even realize why, but I appreciate your comments more than anyone. I can understand them, and relate most to field situations. >>Lets see, what it V = I*R, I = V/R or R= V/I? Just kidding. Likely you can write your own formulas. I can write some but I like to have them programmed into my HP 15 C. Very fast and often saves me hundreds of dollars, in a few cases, thousands of dollars. Yep, I evaporated the entire shaft of a screwdriver once when I accidentally got it across the terminals of a car battery. Everyone needs to do it once. I tried to discharge some capacitors in a carrier current transmitter. Surely the power was still on. I hate the think the capacitors could do that with the charge only, but maybe so. Mine did not evaporate, I had a little left. >> It is a somewhat derogatory term Some are transformers, putting out 24 or so volts AC, but most have a diode bridge in them and a filtering capacitor to supply DC. The Wall Warts. faith gagne wrote: What on earth is a wall wart? I wonder if he knows yet. I better make a few statements. Some might think I barely know what one looks like. Nothing could be further from the truth. Likely I have used more than anyone on the list, maybe more than any 10 people unless they sell them, build them, or steal Wall Warts for a living. I don't mean dozens, or even hundreds, I mean Thousands of the critters. Most have a major manufacturers name, fully labeled with all specifications, and the size peaks out at 40 Volt Amps. A few may exist that are 45 or 50 Volt Amps but I have never seen one. If I need 50 VA, 100 VA, or more, I select a chassis mounted transformer, and fuse it as I see fit. The inherent problem, in standby service, it that the larger Wall Warts will come loose from the receptacle. The better and larger ones have a tab with a hole that allows the receptacle cover plate retaining screw to be inserted to hold the Wall Wart into place. My favorite way to install a Wall Wart is to add a receptacle in my own cabinet, which is very convenient for light, drill motor, soldering iron, ect, . and mount the Wall wart inside the cabinet. One system I installed in the mid 70's cost my customer over 10 grand. It was powered by one wall wart. A 40 VA Transformer. No mater the application, I have always disliked the critters for one simple reason. They are a compromised and cheap solution to a problem that in most cases disserves better. A genuine power supply in a plastic or metal case, with a 3 wire grounded plug indicates someone did not cut corners, save a few cents or a dollar or two, and did the job right. Today we use many UL listed power supplies. Most have 4, 6, 8, or more fused outputs. They last 4 to 8 years, 24 / 7 service and deliver the full load they are designed to deliver. When these fail, we never repair them. We replace them with a New Unit. Not that I can't, but when Life Safety and a building full of people, many sleeping, depend on the devices, if something fails, I want it to be something the factory did, ... not something I repaired. Relative to Wall Wart Definitions, . >> It is a somewhat derogatory term About as good as one can get. Power Supply and Transformer are generally accepted terms. They can be from an ounce or two, a pound or two, hundreds or pounds or thousands of pounds in size. Size, use, and origin does not change the definition. I suggest that the proper term be used instead of "Wall Wart". I was going to comment on Fault Current a bit, but this critter is long enough already. Fault Currents are mean, nasty, noisy, dangerous, destructive, explosive, and often kill people. Generally all this is handled at an engineering level, manufacturer labels, various codes, and not of concern to field personnel. Other than, Project Managers, Project Engineers, and Electrical Inspectors. Out of thousands of such people I have known, none run around measuring it. If you measure it, or attempt to do so, it will be the end of most two bit devices. Could be the end of the meter and the end of the user also. Certainly it is not worth measuring on a Wall Wart. I have a 12 VDC power supply that delivers 100 amps. I did design and build a load testing device. This is not the fault current. It has custom heat sinks, sp
Re: CS>Current Measurement, Wheres the Logic ?
Interesting, I had always pronounced it rhyming with palm. Guess that
is what happens when you only see it in print, and never in conversation.
Marshall
Dan Nave wrote:
http://en.wikipedia.org/wiki/Balun
A balun, pronounced /'bæl.ʊn/ ("bal-un"), is a passive electronic
device that converts between balanced and unbalanced electrical
signals. They often also change impedance. Baluns can take many forms
and their presence is not always obvious. They always involve some
form of electromagnetic coupling.
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Re: CS>Current Measurement, Wheres the Logic ?
Wayne Fugitt wrote: Evening Marshall, Likely you can write your own formulas. I can write some but I like to have them programmed into my HP 15 C. Very fast and often saves me hundreds of dollars, in a few cases, thousands of dollars. Uggg, I hate reverse Polish. Never could get my thinking in the proper order to use one effectively. But every other engineer I ever knew loved it. MN -- The Silver List is a moderated forum for discussing Colloidal Silver. Instructions for unsubscribing are posted at: http://silverlist.org To post, address your message to: silver-list@eskimo.com Address Off-Topic messages to: silver-off-topic-l...@eskimo.com The Silver List and Off Topic List archives are currently down... List maintainer: Mike Devour
Re: CS>Current Measurement, Wheres the Logic ?
I thought it was just that southern drawl... ;-))
Dan
Marshall Dudley wrote:
Interesting, I had always pronounced it rhyming with palm. Guess that
is what happens when you only see it in print, and never in conversation.
Marshall
Dan Nave wrote:
http://en.wikipedia.org/wiki/Balun
A balun, pronounced /'bæl.ʊn/ ("bal-un"), is a passive electronic
device that converts between balanced and unbalanced electrical
signals. They often also change impedance. Baluns can take many forms
and their presence is not always obvious. They always involve some
form of electromagnetic coupling.
--
The Silver List is a moderated forum for discussing Colloidal Silver.
Instructions for unsubscribing are posted at: http://silverlist.org
To post, address your message to: silver-list@eskimo.com
Address Off-Topic messages to: silver-off-topic-l...@eskimo.com
The Silver List and Off Topic List archives are currently down...
List maintainer: Mike Devour
