shortbusx
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Post by shortbusx on Feb 20, 2007 16:59:48 GMT -5
Okay, so Ive got my sheilding in place...I did the pickup cavities, the jack hole, the switch plate and chamber.
I got a meter from my dad, and as Ive laid down the copper foil Ive checked the continuity....but I have no idea what Im really measuring? Is it Ohms or what?
Anyways...origianlly I laid down the sheilding in the pup cavities. I measured them and they were all slightly different measurements. I did the chamber...and then the jack hole....all of them measuring differently. BUT then I connected all of these by going through the cables channels and shielding everything together. I took measurements with one probe on one end and the other in different areas and the numbers were consistant and stronger than individually...the more I connected the shielding together the stronger the measurement.
Now what am I measuring? And what does a higher number mean in reguards to my finished project?
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Post by ChrisK on Feb 20, 2007 18:39:09 GMT -5
Hi, welcome a'board. What you want is good conductivity/low resistance between each foil section. I hope that you're measuring Ohms, If your measuring "Whats" I don't know "what" to tell you (especially if what-nots are involved). ;D You need to use the lowest resistance/Ohms scale on your meter. Typically, just touching the probes together will result in a reading of around 0.1 to 0.5 Ohms . The readings between each and all separate sections of the foil should be under 1 Ohm (depending on the intrinsic bulk resistivity of the foil itself). You're essentially creating a copper foil "container/cage" around the circuit.
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shortbusx
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Post by shortbusx on Feb 20, 2007 20:36:27 GMT -5
Ive got the meter turned to the lowest ohm setting, the numbers appear to be high to the left and low to the right...when I touch the sheilding it almost buries the needle to the right...much better reading than just touching the probes together.
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Post by ChrisK on Feb 20, 2007 20:53:14 GMT -5
So, how "deep" is it actually (as in the actual reading)?
Well, you're getting better conductivity when you press the probes to the shield rather than to each other. In reality, the resistance of just the probes and lead wires can't be less than the resistance of the probes, lead wires, and the shielding.
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shortbusx
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Post by shortbusx on Feb 20, 2007 21:03:53 GMT -5
I'll make notes tonight on the readings.
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Post by UnklMickey on Feb 20, 2007 21:32:38 GMT -5
...Well, you're getting better conductivity when you press the probes to the shield rather than to each other.... it shouldn't be hard to understand why. OO O)=(O
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shortbusx
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Post by shortbusx on Feb 20, 2007 21:47:20 GMT -5
<~~~Doesnt know(remember) ANYTHING about Ohms law
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Post by UnklMickey on Feb 20, 2007 22:13:45 GMT -5
doesn't really need to..............
my hint was about shape and contact.
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shortbusx
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Post by shortbusx on Feb 20, 2007 22:21:33 GMT -5
So then why did my readings get better with the more area that was shielded?
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Post by hammeroff on Feb 20, 2007 23:03:53 GMT -5
If your measuring Ohms, you're getting more because the copper is providing more resistance the more area electrons need to pass. Let's say "R" is your total resistance (Ohms) p is the resistivity of copper L is the length electrons need to pass A is a cross sectional area of the wire R=p*(L/A) Being that p and A are being held constant, as you increase L, R goes up. Don't worry about it too much As long as your checking for Ohms, and you get a reading, you've got continuity, and the beast should be quiet.
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shortbusx
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Post by shortbusx on Feb 21, 2007 17:54:48 GMT -5
Well as it turns out, this borrowed tester and I are getting inaccurate readings. Turns out the probes give erratic readings sometimes...I figured this out last night. I get about the same readings from touching the probes together as reading my shielding...and its like it needs to be calibrated too.
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Post by ChrisK on Feb 21, 2007 22:26:44 GMT -5
And I thought that you were just drawing dirty pictures again. 'Cuz yer increasing the contact area as opposed to the very small area when just the probes are touched together. This effect will vary as a function of the cross sectional area of contact and the pressure applied thereto. Because there is more conductivity (less Ohms) as the conduction path gets broader. Yep, both should be nearly zero. Yep, since this is ooooold analog meter technology, that little screwdriver adjust thingy in the bottom middle of the meter face is adjusted for a zero reading (use the volt DC scale for this). Have your father do this (it's his meter). Also, since this is ooooold analog meter technology, you probably ain't gonna be able to reliably read near zero anyway. If you read nearly the same values as when the probes are touched together when you measure the individual shield sections for continuity, you're all good. Words like better, buried, deeper, and stronger are all meaningless without definition. You want a low Ohms reading (as in 2 or less since it's copper) between every and all sections and connected circuits. I'm also assuming that you used solder to connect the sections and associated circuits wires. So, better is actually a lower Ohm reading (we're looking for increased conductivity here). Conductivity (mho) = 1/Ohms
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