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Old 4th September 2012, 11:25 PM   #27271
bcarso is offline bcarso  United States
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Quote:
Originally Posted by wayne View Post
I suppose I should stop using my mouth as a third hand for solder. Probably explains a thing or two. Lead is all natural though just like Plutonium, Arsenic and hemlock.
As Chris Knight (Val Kilmer) says in Real Genius: "In the immortal words of Socrates, 'I drank WHAT?' "
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Old 4th September 2012, 11:40 PM   #27272
wayne is offline wayne  United States
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I forgot you could have your blood tested for Lead. One of our employees did and she was fine even before lead free but we do have a exhaust system in production. I guess it can be removed by chelation (SP?) therapy if my memory is correct.
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Old 5th September 2012, 01:52 AM   #27273
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Originally Posted by bcarso View Post
It would be interesting, possibly horrifying, to be able to find out what happened to some of the people who worked soldering cad-plated chassis with lead-bearing solder for my father's companies over the years. He himself used to carry bits of Pb-Sn solder around in his pockets along with change and car keys.
Mad hatters all.
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Old 5th September 2012, 02:38 AM   #27274
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Originally Posted by SY View Post
What does Plotnicki use?
I'm shamed, I agree with too much of his restaurant criticism.

(Sorry for the OT)
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Last edited by scott wurcer; 5th September 2012 at 02:45 AM.
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Old 5th September 2012, 02:46 AM   #27275
bcarso is offline bcarso  United States
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Originally Posted by scott wurcer View Post
Mad hatters all.
It's paradoxical that the Winged Messenger should be associated with dementia.
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Old 5th September 2012, 02:47 AM   #27276
RNMarsh is offline RNMarsh  United States
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Solder.... Lead. Mercury. Anyone worried about their old tooth fillings?
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Old 5th September 2012, 02:58 AM   #27277
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Originally Posted by RNMarsh View Post
Solder.... Lead. Mercury. Anyone worried about their old tooth fillings?
The reason that Gold has such high value
is primordial memories of it's ingestion.

Last edited by hitsware; 5th September 2012 at 03:04 AM.
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Old 5th September 2012, 07:06 AM   #27278
SY is offline SY  United States
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Quote:
Originally Posted by RNMarsh View Post
Solder.... Lead. Mercury. Anyone worried about their old tooth fillings?
Only those with no particular knowledge of chemistry and a willingness to believe quacks.
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Old 5th September 2012, 10:14 AM   #27279
bcarso is offline bcarso  United States
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I once swallowed the mercury in a thermometer as a child. My father was assured that they didn't use mercury anymore, but that was reassuring nonsense.

I guess that accounts for why I am so stupid today. Or at least mad as a hatter.
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Old 5th September 2012, 01:12 PM   #27280
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Quote:
Originally Posted by gpapag View Post
You at least try to provide some explanation.
Some others take it for granted.
I will ask. The BH curve nonlinearity and the permeability’s dependence on H field strength are phenomena known on x-former cores.
Assuming audio x-formers (input, coupling, output) have been used, studied and optimized for decades, where is the data quantifying the harmonic distortion generation due to these nonlinearities of ferromagnetic materials? (links, reference)
I would have to google for links, I do not have any available.

However, that said..Amperes law states the magnetic field (B) around an electric current is proportional to that current. And Faraday's law states that the voltage generated in a loop of wire is proportional to the rate of change of (B) flowing through the loop.

Neither law invokes H, so if H is a non linear function, it does not directly impact either Ampere's law nor Faradays. So that's how I'd explain it, if I knew what I was talking about...

The non linearity of a BH curve will certainly impact the inductance of the system, and when you start to saturate, that inductance will drop. All these factors will come into play with the primary current, so the IR drop and varying impedance of the primary to its driver can cause all kinds of nasties..

BTW, I looked up hyperphysics to confirm what I've said w/r to Ampere and Faraday..really nice site, University of Georgia I believe..

Quote:
Originally Posted by gpapag View Post
The shielding effect a metal provides on magnetic fields, is more or less achieved by the eddy currents generated within it.
For all conductive shields, you are correct. Materials with a relative permeability above 1 will start to direct the magnetic field along the metal bulk also. Unfortunately, as the field increases, the permeability will change, this is the distortion part.. Mu metal, while extremely high in relative permeability, saturates at very low levels. At half a tesla, it's useless. At half a gauss (earths magnetic field approx..) it's great, you can make a zerofield box really easy..

BTW, when a sheet of magnetic material is conducting time varying currents, as the frequency rises, the current density profile will change. At higher frequencies, the current will pinch to only part of the sheet, that path being the path which provides the lowest system reactance. If that path goes past sensitive input circuitry or ground reference wires going to the system star, oh well.

Unfortunately, in the days of vacuum tubes and high impedances, that was not so prominent. Once we went solid state and low impedances, this effect really raised it's ugly head.

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Originally Posted by gpapag View Post
Therefore, for low freq. fields (50/60Hz and harmonics), substituting non ferrous for ferrous shields, one has to increase the shield thickness two to four orders of magnitude for to achieve equal shielding effects.
Absolutely accurate.
Quote:
Originally Posted by gpapag View Post
Rel. distance: By old ARRL handbooks, the distance of a metal shield from a HF coil had to be minimum 3 coil diameters for the Q of the coil to be affected by less than 10% (from memory).
Accurate as well in concept, I don't have the ARRL handbook. The Q in that application will depend on the combination of inductance and reistance of the coil. Using a standard Ls/Rs model, the Rs is the in phase loss of the system when driven sinusoidal. This measurement is also dependent on the losses caused by materials nearby which create eddy current losses. So for any inductor, proximity to a non ferrous metal will lower the system inductance, and raise the system losses. Modification of Q as it were.

jn

Last edited by jneutron; 5th September 2012 at 01:38 PM. Reason: done with fixing my mistakes..
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