Carl, your humor is best class ....“the major cause of problems is . . . solutions.” On 12 August 2016 at 15:34, Carl Van Wormer <[log in to unmask]> wrote: > #4 - Our customer is assuming the noise problem cannot be solved at the > noise source. They do not have control of the motors and VFD motor drive > that may be attached to their systems, so the variety of the noise sources > may be infinite. > > > > #3 - I do not assume the solution will be easy or even guaranteed, but the > initial experiments in balancing the trade-offs shows promise. > Implementation gets me into the realm of “the major cause of problems is . > . . solutions.” > > > > #2 – After I explain my job to somebody and how I enjoy my work week, I > usually end with “. . . and they pay me for it!” > > > > > > I’m glad it was a slow TechNet week, allowing me to receive a lot of > attention and suggestions. > > > > 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] http://cipherengineering.com > > > > > > *From:* Inge Hernefjord [mailto:[log in to unmask]] > *Sent:* Friday, August 12, 2016 12:54 AM > *To:* TechNet E-Mail Forum <[log in to unmask]>; Carl Van Wormer < > [log in to unmask]> > > *Subject:* Re: [TN] looking for medium resistance material > > > > Carl, > > !. Admire you. What you do is real engineering. > > 2.You must have rare position and a generoujs boss. > 3.I hope you are aware of how easily time and contract runs away. You may > meet unexpected obstacles on the way to a tested an d approved component. > 4. You did not react on my q wheater you could solve the problem by > minimize the noise at the source. > 5. You present , very openly, details that already may have been sent back > to the Big Copiator. You may be on a hot spot, noise reduction is one of > the most discussed topics in the SPACE industry, meterology, Medecine and > other Hitech industries. Just a reminder....don't give 'them' to much > goodies... > > / Inge > > > > On 11 August 2016 at 18:06, Carl Van Wormer <[log in to unmask]> > wrote: > > Since it's a slow TechNet morning, I thought I'd give an update on my > recent experiment: (feel free to delete if you have real work to do). > > I obtained a sample of metalized Mylar that was hiding inside of a 3uF > yellow capacitor. I prepared a test capacitor made from two 1" square > pieces of Copper tape attached to two business cards (for insulation and > alignment) and then ran some 30 gauge wires from opposite corners for > measurement attachment leads. I named these two cards plate #1 and Plate > #2. I prepared a third business card with 2" square of Copper tape (shield > #1), a fourth card with a 2" circle of a shiny metal stick-on silver award > star (shield #2), and a fifth with a 2" square of the metalized Mylar from > the sacrificial capacitor (shield #3). I stacked up the test jig with the > sandwich of plate #1, shield #1, and plate #2, and then measured about > 10pF. When I connected the guard terminal of my ESI VideoBridge 2100 to > shield #1, the capacitance reading dropped to about 0.2pF, showing that the > shielding was effective. Repeating the measurements with the silver star > and the capacitor film shields gave similar shielding effectiveness. It > was difficult to make a reliable connection to the capacitor film, but when > the contact was made, the shielding was effective. > > Capacitive shielding effectiveness: Good! > > To test the effect of the shield material in a magnetic field, I used the > two ferrite cores and a 100-turn coil similar to the final product. The > cup-cores are separated by about 1mm, and my business cards are about 1/3mm > thick. Measuring the inductance of the coil in the cup-cores with a > 3-business-card spacers in the gap, I got an inductance of about 780uH with > Q=77. Inserting the Copper tape card (shield #1) in place of one of the > spacers gave me an inductance of 255uH with Q=2.5 (the Copper is acting > like a shorted turn). Similar testing of the silver star sticker (shield > #2) gave an inductance of 630uH with Q=2.9 (I guess the metal on the > sticker is thicker than I thought). When I inserted the card with the > metalized Mylar (shield #3) into the gap-stack, the inductance measured > 760uH with Q=68. This showed very little degradation to the magnetic > system. > > Magnetic transparency: Good! > > Metalized Mylar shows great promise as a solution to my problem, probably > because the thickness is quite thin compared to the calculated skin effect > depth of about 0.08mm at 1MHz. > > Now the problem comes down to making a reliable electrical connection to > the metalized Mylar. I am open to any suggestions as to effective ways to > physically connect the metalized Mylar to my system, for positional and > electrical attachment of the shield. I'm hoping to hear of proven > techniques (Conductive epoxy, ultrasonic welding, etc.) that have been > successfully used for reliable electrical and mechanical mounting and > attachments. > > 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] http://cipherengineering.com > > > -----Original Message----- > From: Carl Van Wormer > Sent: Wednesday, August 10, 2016 7:42 AM > To: TechNet E-Mail Forum <[log in to unmask]> > Subject: RE: [TN] looking for medium resistance material > > I found that a capacitive shield plate connected to ground through a 100 > Ohm resistor would eliminate the VFD noise effects. Changing the resistor > to 1000 Ohms started to show some interference. I'm hoping that a flimsy > Mylar conductor (around 1 Ohm per square) would be a sufficient shield for > the electrical field coupling (the gap between the 2 coils is a couple of > mm). > > As the old guy in the ESI repair department would say . . . "One > experiment is worth a thousand expert opinions." > > 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] http://cipherengineering.com > > > -----Original Message----- > From: Louis Hart [mailto:[log in to unmask]] > Sent: Wednesday, August 10, 2016 7:28 AM > To: TechNet E-Mail Forum <[log in to unmask]>; Carl Van Wormer < > [log in to unmask]> > > Subject: RE: [TN] looking for medium resistance material > > Carl, if the conductor thickness is less than the skin depth, would that > mean the magnitude of the evanescent wave electric field would be great > enough to allow propagation outside the shield? Sorry to say, my > understanding of electromagnetic field theory is a lot less than what I > think it should be, but I am curious. > > Regarding aluminum and soldering, I knew a guy who had a roll of 'aluminum > solder' on his desk although I never saw him use it. The wire was several > millimeters in diameters, so may not have been for electronic purposes. > > On the subject Drew brought up of mu-metal, I inherited a microwave > spectrometer long ago which had a klystron housed in the stuff. The fellow > who bequeathed it to me said the metal was great for shielding, but its > desirable properties were degraded by mechanical forming. > > Nice to see good activity on TechNet. (I may qualify as one of the > old-timers, having joined when it first appeared back in 1994 or 1995.) > Louis Hart > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl Van Wormer > Sent: Wednesday, August 10, 2016 9:16 AM > To: [log in to unmask] > Subject: Re: [TN] looking for medium resistance material > > My next attempt will be to try a metalized Mylar, hoping that the thin > conductor (much thinner than the skin effect depth) will be good enough for > the capacitive shielding, but too thin for significant eddy current flow > from the magnetic field. If that work, I will be left with the "simple" > matter of connecting to the shield. How do you solder a wire to a party > balloon? > > 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] http://cipherengineering.com > > >