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. > > > > > > >