Merideth,, If you do layers, it's very important they don't come into physical contact with each other. Some "bubble wrap" will do. Regards, Erich -----Original Message----- From: meredith lambTo: psn-l@.............. Date: Tuesday, June 13, 2000 9:05 PM Subject: Re: Another mu-metal/permalloy question (and magnetometer note) ChrisAtUpw@....... wrote: > If you had two concentric spheres, you would be able to apply a higher > external magnetic field before it started to penetrate the inner sphere. > > For your apparatus, I think you need an outer shield of Permalloy etc. to > reduce the effect of the low external fields and an internal shield to screen > the Permalloy from the core magnets. This shield might be silicon iron or you > might get away with mild steel. You might need two layers. > > Hope this qualitative description helps. > > Chris Chapman Chris, David, Al and all, Many thanks for the email replys to my original question, I've picked up your thoughts on it, and think I have a sufficient understanding now. Lacking alot of lab equipment for all this, about all I can do is perhaps apply some ribbon permalloy material to a shield and observe over time. With time I hope to have a second diamagnetic machine on line, and with both pointed in the same direction, one could be unshielded, and then a more visual comparison could be made with the SDR recording and perhaps additionally to a regular coil/magnet as the prospective "ideal". The most practical approach is too add layers if needed. ***************************************************** MAGNETOMETER THOUGHTS With reference to a magnetometer which uses a "string" and a magnet, its possible to use acouple layers of diamagnetic graphite with the magnet simply levitating in between (a regular diamagnetic stand, with overhead magnets). Of course it might need a reflective first surface mirror on a end of the single or multiple cluster of magnets for output (or other transducer means). Providing the graphite is diamagnetic enough and their is a stable temperature environment, and its far enough away from metallic/magnetic influences, it might suffer less temperature effects than is found possibly with a support "string" in the type previously mentioned. If the east -west orientation is desired, than another magnet could be placed nearby. A normal diamagnetic "stand" or machine is sensitive to temperature; but its in the vertical plane. I never tried this with my material in the city environment, and of course the goal was make a seismometer, so I added diamagnetic side "wedges" of graphite to limit its normal North-South or magnetic attraction to household items. Thanks again for all the generious help, from you all. Meredith Lamb __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>