Theories about coil-shielding

[maikl]

Here's how he did ...

[maikl]

And this

[6666]

Been playing with difference amplifier lately for IB coils,

Green would you mind sharing the design you have been playing with please ? thanks

[green]

[Green would you mind sharing the design you have been playing with please ?]

I want to try another design first. Will share when I have one I'm happy with, soon I hope. I'm still learning, haven't built a PI detector yet, not sure how the amplifier will operate off the bench.

[6666]

Ok thanks Green

[baum7154]

Not suggesting aluminum foil is the way to go. A plot showing why I think it didn't change the 9 inch coil sensitivity. First image is a 2x2 inch piece of aluminum foil not cut and cut in a pattern shown in second image The cut foil has a TC of .4usec vs 3usec for the not cut.

Fascinating result from just cutting! It is always important to specify the thickness of the foil as this has the largest effect on T/C. Do you know how thick it is?
It would be interesting to see how a piece of foil at a specified thickness, cut as you describe, and long enough to do your 9" coil comes out on the T/C test. We know that long rectangular strips do have an effect of increasing T/C in addition to the thickness per our discussion in the Target Time Constants thread. It would be interesting to compare one with the cuts versus one without the cuts.

Good Stuff!

Dan

[green]

It was regular Reynolds aluminum foil. All I have is a vernier calipers. I folded a piece a few times and measured it to be about .001. Not sure how to measure a piece that long but a will try some different length pieces. Maybe some with more cuts/inch. Was looking at my copy of ITMD and saw a section on cutting targets. Might be where I got the idea to cut the foil.

[baum7154]

Regular Reynolds foil is about .001" thick

[Waikiki_Sweep]

Measure some length of foil than weight it on jewelers scale. If you know density of aluminum you can calculate thickness.

[green]

Another plot. Cut four pieces, 3/16 x 2, 3/8 x 2, 3/4 x 2, 3/2 x 2 inches. The 3/16 x 2 measured the same TC as the 2 x 2 inch piece cut in a 3/16 pattern. I'll try a longer cut piece the next time I cut one

[green]

Another plot that I think shows pattern length might not make a difference.

[Henrikras]

I know that this has been said a hundred times, with different mixtures. But this is my first test with Graphite powder and some Alcohol and to me it seem to Be a easy way to make a shielding. Just mix the powder with the alcohol and paint it with a brush.
I made this video. http://m.youtube.com/watch?v=SqM6eWwLIUs

Henrik.

[Aziz]

I know that this has been said a hundred times, with different mixtures. But this is my first test with Graphite powder and some Alcohol and to me it seem to Be a easy way to make a shielding. Just mix the powder with the alcohol and paint it with a brush.
I made this video. http://m.youtube.com/watch?v=SqM6eWwLIUs

Henrik.

Hi Henrik,

a good binder (resin) for alcohol is shellac. Some flakes of it solved in alcohol with graphite powder is a nice graphite painting mixture.
http://en.wikipedia.org/wiki/Shellac
This should give a much tighter graphite shielding layer.

Cheers,
Aziz

[Silver Dollar]

I'm not sure you can buy that anymore. "shellac was one of the dominant wood finishes in the western world until it was largely replaced by nitrocellulose lacquer in the 1920s and 1930s."
Mmm food glaze, should make some tasty coils!

[greylourie]

French polishing uses "shellac flakes". A google brings up a number of vendors.