Mylar rescue blankets, from where?

[Mullihaka]

I have bough several of those for shielding purposes, but they all have the same problem: the metal layer is between plastic layers, so I can't get a connection.

Does anyone have trade names for rescue blankets, where the metal is in the surface?

European one's preferred (for easier delivery).

[bklein]

I wonder if acetone would remove plastic on one side of the foil so you could attach a contact by pressure or silver epoxy?
Wouldn't just taking shielding from a USB cable work as well?

[Dennis the Mennis]

I have bough several of those for shielding purposes, but they all have the same problem: the metal layer is between plastic layers, so I can't get a connection.

Does anyone have trade names for rescue blankets, where the metal is in the surface?

European one's preferred (for easier delivery).

Hi Mullihaka ,

I had the same problem (I think so)

Bought a rescue blanket : but no conduction .
Tried to remove the toplayer, if there was any , with sandpaper : no conductivity .

Took my Multimeter to a store and measured the resistance before I bought the blanket : no conductivity so no deal .

So bought another blanket from another brand , took me some while ... , same problem !

A hobby may cost something ...

Then I tried to measure it not with the probes of the multimeter pinned into the surface ( very small contact surface ) but with the probes 'flat' on the blanket making the biggest contact surface . ( sideways )

This worked for me on both blankets .

I hope this makes sense

The conductivity wasn't that high but it should work , haven't tried it for shielding myself yet.

At least I have enough Mylar for a lifetime making coils

I remember DFBowers bought his blankets in a supermarket for cheap ( as in 1$ )

I've payed a couple of Euro's so a more expensive blanket isn't any better .


Hope this helps , let me know !!!


kind regards ,

Danny

[Mullihaka]

Hi DtM,

It works, thanks! I pressed two coins on the mylar and measured the resistance that way.

Strange thing is, that occasionally it gives me close to zero ohms, but most of the time unstable values. I examined the mylar with a microscope with 100x magnification and couldn't see the reason why.

I tried Acetone and gentle scratching with a sharp knife, but that didn't help at all.

Next, I'll shield the coil with mylar, then take bare copper wire and make it's surface a bit rough with sand paper. Then, tight wrap of ten turns at the beginning of the shielding. Then the same in the other end of the shielding and resistance measurement between the copper wires.

I wonder if the rescue sheet is the same everywhere. Wouldn't the metal strip off too easily if not coated with mylar?

[soverey]

I have bough several of those for shielding purposes, but they all have the same problem: the metal layer is between plastic layers, so I can't get a connection.

Does anyone have trade names for rescue blankets, where the metal is in the surface?

European one's preferred (for easier delivery).

You may try the first aid kit or the car ,there is usually a rescue blanket in them.

[SVEN1]

I bought some of this copper shielding tape with conductive adhesive:
http://cgi.ebay.ca/ws/eBayISAPI.dll?...m=260990793350

[bklein]

I suspect the "conductive adhesive" is collective terminology for thin adhesive. To be truly conductive it would have to contain conductive particles and I don't think they do. I've messed with such tape for EMI reduction purposes. For example, take an ohm meter and connect one probe to the copper and another drag lightly across the adhesive side. I think it makes contact only when it is pushed aside and the probe hits the other copper side. No matter really though - for this a tape without adhesive would be fine...

[SVEN1]

I suspect the "conductive adhesive" is collective terminology for thin adhesive. To be truly conductive it would have to contain conductive particles and I don't think they do. I've messed with such tape for EMI reduction purposes. For example, take an ohm meter and connect one probe to the copper and another drag lightly across the adhesive side. I think it makes contact only when it is pushed aside and the probe hits the other copper side. No matter really though - for this a tape without adhesive would be fine...

Actually, just touching the adhesive with the probe and touching the copper side makes connectivity. You do not have to push the probe in. If you tear two pcs of the tape and press them together then touch probes to each pc. copper or adhesive sides, connectivity is made.

[Dennis the Mennis]

Hi DtM,

It works, thanks! I pressed two coins on the mylar and measured the resistance that way.

Strange thing is, that occasionally it gives me close to zero ohms, but most of the time unstable values. I examined the mylar with a microscope with 100x magnification and couldn't see the reason why.

I tried Acetone and gentle scratching with a sharp knife, but that didn't help at all.

Next, I'll shield the coil with mylar, then take bare copper wire and make it's surface a bit rough with sand paper. Then, tight wrap of ten turns at the beginning of the shielding. Then the same in the other end of the shielding and resistance measurement between the copper wires.

I wonder if the rescue sheet is the same everywhere. Wouldn't the metal strip off too easily if not coated with mylar?

Hi Mullihaka ,


I experienced the same thing measering the conductance : unpredictable behaviour .

It's a hard job to measure about 300-400 ohms on a strip with 2 meter length , the next moment the multimeter is giving infinite.

And only conductance on the 'golden' side of the blanket , the silver side is completely isolated.

Perhaps there is somebody with 'Mylar' experience to comment on these questions?

I have non on this subject , it is on the experiment list...

I'm very curious


kind regards ,

Dennis the Mennis

[DOOLEY]

conductive mylar

hello all,

regarding the rescue blankets made of conductive mylar,for lucky people in the uk,

go to your local pound land and they are there in the camping area.

so spent £1 and tested them, one side is 8 ohm's per inch with just bare probes,

the other side is non conductive.

well , thats everyone in the uk sorted then.

oh yes , and it's really thin stuff , but hard to rip , i tried , it just stretches.

so , the question remains , is 8 ohm's an inch to low ??

whats the "IDEAL" resistance ?? or don't it matter ??

[satdaveuk]

Bought 2 lots from a camping store which were about £2.50 each, but the problem remains that if you have to run a bare wire around the coil your trying to shield because your not sure of o/cs within the mylar then what good is it, if you got 2-3" where your getting continuty then the next inch your either very high or open circuit, hence why everyone i know on here thats used it have had to run wire throughout the coil.
That tells me stright away you have a unbalanced shielding at the very least, so what good is that? Symtoms in the field falsing couldnt use anymore than just below halfway with TGSL with both builds
Maybe in some of your countrys you will get away with it but here in the uk you will not, Ive proved it with many tests earlier in the year.
However' if any of you have managed to get hold of thin mylar that you can measure from end to end after wraping around the coil without any wires at each end then i would say your proberly have one of the best coil diy shielding todate.
The best coil and housing shield ive used thats constant and you can add or takeaway resistance which is quite cheap is synthetic graphite mixed with boat varnish 1:1 and a splash of turps, each end with copper 10mm tape thats it.
The best resistance for Ivonics TGSL project using in the UK is 2kohms per inch, which is 2-3 coats brushed on. No falsing well past halfway with sense control and no noticeable lack of sense on both builds, the proof is in the field the real world of metal detecting.

Regards

[Davor]

I bought some of this copper shielding tape with conductive adhesive:
http://cgi.ebay.ca/ws/eBayISAPI.dll?...m=260990793350

Gee, if this thing contains real copper - it is an instant coil by itself. It may be worth investigating

[Mullihaka]

I found another way to check, if the rescue blanket is conductive enough for shielding. First, I wrap the blanket strip around the coil and then wrap ten turns of bare wire over it.

When done, I measure the capacitance between the bare wire and one end of the coil. That I compare to the value of a plate capacitor, taken form the calculator: http://www.daycounter.com/Calculator...lculator.phtml

The coil bundle diameter, dimensions of the shield, coil circumference and thickness of the insulating tape can be measured. The dielectric constant of the tape can be estimated based on figures given on the calculator page. The common insulating tape should be close to polyethylene (2.25).

[golfnut]

I read an article by a guy who had been around metal det design for years and he said

10k ohms per square gave the best results!

Ive only used cooking foil.

What do whites use - they wont sit wrapping foil and messing about cutting suvival blankets.

Just do what vendors do now. Dont need to re invent the wheel then!.

Anyone opened a broken coil of suitable type?

S

[Qiaozhi]

I read an article by a guy who had been around metal det design for years and he said

10k ohms per square gave the best results!

Ive only used cooking foil.

What do whites use - they wont sit wrapping foil and messing about cutting suvival blankets.

Just do what vendors do now. Dont need to re invent the wheel then!.

Anyone opened a broken coil of suitable type?

S

I think most of the major manufacturers use graphite on the inside of the coil shells. The ones I've measured are around 100 to 200 ohms across the diameter. The Garrett Crossfire shells use an electrostatic sheet on the top and bottom of the coils, and the shield is connected using a simple spring arrangement.

This is what I use ->
http://www.maplin.co.uk/aluminium-tape-4098
You can also get 20um tape elsewhere.