Hi Inge,
Been a while since I heard the term Mu-metal. Very associated with noise suppression in tube equipment.
Drew
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Wednesday, August 10, 2016 3:09 AM
To: [log in to unmask]
Subject: Re: [TN] looking for medium resistance material
Gosh, TN isn't declining as I thought. Your challenge seems to place in a research lab. When I ran into ssuch problems and the solution proposals grew until I couldn't decide which one to test (as usual you are expected to do the job over a night and with no money) then I use go back and ask myself if there might be another concept. Background noise is a plague and many a time nearly impossible to eliminate. Therefore I wonder if not the cheaapest and fastest way is to modify the noise source. B&O had a similar issue with their studio recorders. They eliminated the problem by encapsulate the motor in my-metal. The S/N lowered by one magnitude. Just a thought. Labbing with various resistiviity stuff can be expensive a case.../Inge
On 9 August 2016 at 17:11, Carl Van Wormer <[log in to unmask]>
wrote:
> The longer story is (feel free to ignore this if you don't care about
> the background details):
>
> My short term goal is to set up an experiment to see if a shield of
> intermediate resistance will address my present condition. We all
> know that the major cause or problems is . . . solutions.
>
> The inherited problem system is used to transfer power (5W-10W) during
> Phase 1 of operation, and to transfer acoustic signals (Piezo pickup,
> 10kHz to 1MHz) daring Phase 2 of operation. The 100 turn, 15mm
> diameter coils were mounted inside of ferrite cup-cores with a gap
> between the 2 halves of the cores. One core-half was mounted in a
> fixed aluminum housing, while the other was mounted in an aluminum
> housing at the end of a rotating shaft (on axis) with a gap between the cores of about 1mm.
>
> I came in to solve a noise pickup problem on the received acoustic
> signal which was caused by a VFD motor speed controller. The symptoms
> could be simulated on the bench by connecting a 3kHz, 5V signal
> generator square wave to the rotating housing. In the classic “fix
> it, but don’t change hardly anything” request, I found that I could
> shield the receiving coil (inside the core) with some copper foil tape
> (leaving a gap to avoid the “shorted turn” effect). This eliminated
> the effect of the capacitive coupling on my test bench. During the
> implementation phase, I found that we still had some noise that was
> traced to the capacitive coupling on the rotating (source) side.
> Since the coils were not differential (one end of each was connected
> to local ground), the asymmetrical coupling signal caused a current to
> flow in the transmitting coil that magnetically coupled to the
> receiving coil. Adding a shield to the rotating coil addressed that noise injection method. The system was pronounced “Good.”
>
> We have found that the Phase 1 power transfer efficiency is reduced in
> the shielded systems. Eddy current losses in the shield seem to be
> the cause, so I’m looking for ways to reduce those losses in my
> environment. Raising the resistance of the shield material seems to
> be a simple solution, as long as the resistance is low enough to provide effective shielding.
> Unfortunately, I’ve been unable to find some easy to acquire samples
> of various resistive sheets to play with. I was hoping to do some
> easy experiments to see if my resistive based shielding approach
> stands up to my first set of experiments before I started the process
> of defining a material to be used. I’ve found some conductive ABS
> filament (
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.makergeeks.com
> _coabs3dfi10.html&d=CwIFaQ&c=qI44ipyoBm0hVwhmy07quvdiOJrWojxKI35ez1PFJ8U&r=HZgy48l2HWBqJDpR-HiPKjp95VqM-oQXPmkYZLVMvsY&m=2Kltqw4Q9aTjEqsGaI_UBTgPBVkMDZWnQDFo8GjJ22w&s=Y2ZkYLmy0oTLWywZdGSL-A0HuKDw8qUArO8gW4sQh2w&e= ) that might work if I can find somebody to print a plate and a method to electrically connect to it, but I don’t know a local friend with a 3-d printer.
>
> I’m still hoping for the sample kit of sheets of various resistivity
> materials, but I haven’t found the right page in the Digi-Key catalog . . .
>
> Thanks for any suggestions,
> Carl
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> Sent: Tuesday, August 09, 2016 5:55 AM
> To: [log in to unmask]
> Subject: Re: [TN] looking for medium resistance material
>
> There is just about every type of material with just the right
> properties you are looking for available as a 3d printing medium.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
> Sent: Tuesday, August 09, 2016 12:44 AM
> To: [log in to unmask]
> Subject: Re: [TN] looking for medium resistance material
>
> Very kind of you Inge, but this is not really my cup of tea these
> days. I am aware that there are a number of suppliers of carbon based
> inks and these can be tailored to produce desired sheet resistivity
> ranges. That sort of thing is widely used on flex circuits and
> additive (printed
> electronics) circuitry. I would think internet searching should bring
> up a good candidate list of suppliers in a few iterations . There is
> cross over here to ESD protection products, so that would be a good search area also.
>
> ---
> Regards
>
>
> Mike
>
> www.chrisfennerfund.org
> www.facebook.com/chrisfennerfund/
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
> Sent: Sunday, August 7, 2016 10:37 AM
> To: [log in to unmask]
> Subject: Re: [TN] looking for medium resistance material
>
> Carl,
> when I was active I used to contact SemiAlloys. I needed certain
> resistivity in lids for resistivity pulsed current seam welding of
> small packages for missiles. We produced about 50,000 pcs from
> SemiAlloys with
> He/Kr10 exp -10 with succcess. Mike Fenner has more to say , I think..
> They are extremly nice to cooperate with. Mike as well, despite he is
> english.
>
> Semi Alloys Inc
>
> 888 S Columbus Ave
>
> Mount Vernon, NY 10550
>
> (914) 664-8318)
>
>
>
> Good Luck / Inge
>
>
> On 7 August 2016 at 05:40, Carl Van Wormer
> <[log in to unmask]>
> wrote:
>
> > I usually want my physical structural resistances to be as low as
> > possible
> > (conductors) or as high as possible (insulators). Now I need an
> > intermediate resistance, probably in the range of 100 to 1000 Ohms
> > per square. The application will be an electrostatic shield in an
> > alternating field, hopefully balancing magnetic heating losses
> > against capacitive shielding effectiveness.
> > I have never seen these materials offered from any of my normal
> > sources, but I’m sure that there is something out there that will
> > work. It could be sheet materials, paints, or slightly conductive
> > epoxies, or something else I haven’t thought of. Since there is a
> > very wide experience base on this site, I’m asking here first.
> > Any suggestions will be appreciated.
> >
> > Thanks,
> > Carl
> >
> >
> >
> >
> > Carl B. Van Wormer, P.E., AE7GD
> > Senior Hardware Engineer
> > Cipher Engineering LLC
> > 21195 NW Evergreen Pkwy Ste 209
> > Hillsboro, OR 97124-7167
> > 503-617-7447x303
> > [log in to unmask]<mailto:[log in to unmask]>
> > https://urldefense.proofpoint.com/v2/url?u=http-3A__cipherengineerin
> > g.com&d=CwIFaQ&c=qI44ipyoBm0hVwhmy07quvdiOJrWojxKI35ez1PFJ8U&r=HZgy4
> > 8l2HWBqJDpR-HiPKjp95VqM-oQXPmkYZLVMvsY&m=2Kltqw4Q9aTjEqsGaI_UBTgPBVk
> > MDZWnQDFo8GjJ22w&s=dMBT6QlK9T4sE3Ip5GFDjIUpFBLBGdqSiF_o3PdX0mY&e=
> > <https://urldefense.proofpoint.com/v2/url?u=http-3A__cipherengineeri
> > ng.com_&d=CwIFaQ&c=qI44ipyoBm0hVwhmy07quvdiOJrWojxKI35ez1PFJ8U&r=HZg
> > y48l2HWBqJDpR-HiPKjp95VqM-oQXPmkYZLVMvsY&m=2Kltqw4Q9aTjEqsGaI_UBTgPB
> > VkMDZWnQDFo8GjJ22w&s=nZ5vCiC3GCRNBuw_ppMIR3xbH_lsz8xzwcyxdDP4Uwg&e=
> > >
> >
> > This message may contain confidential and/or proprietary
> > information, and is intended for the person/entity to whom it was
> > originally addressed. Any use by others is strictly prohibited. If
> > I sent this to you by mistake, please be nice and delete it, and
> > then tell me of my mistake so I can send it to the right person.
> >
> >
> >
>
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