PSN-L Email List Message

Subject: Re: magnet info
From: CapAAVSO@.......
Date: Sat, 22 Jul 2000 09:33:03 EDT

In a message dated 7/19/00 1:52:33 PM Eastern Daylight Time, sean@........... 

<<  I have found a useful source of magnets in the McMaster Supply
  catalog (; 3000 page catalog 630-833-0399).
  They have two pages of Alnico-5 and Alnico-8, and another two
  pages of rare earth magnets and ceramic multipoles. I am using a 
  bonded neodymium ring magnet for a new feedback transducer.
  I think that their offering is more complete and consistent 
  than Edmund Scientific. THey have some rather large offerings >>


Thanks for the above information. McMaster has a huge offering of magnets 
available, an order of magnitude more than Edmund Scientific. I found just 
what I wanted to replace the rather temperature-sensitive "Wondermagnet" 
Neodymium magnets I was using on my McWilliams torsion-balance magnetometer. 
Alnico magnets are much less temperature sensitive than the rare earth 
magnets. I ordered an Alnico 8 magnet 3/8-inch diameter by 4-inches long. 
Alnico 8 has a lower temperature coefficient than the more commonly available 
Alnico 5. For my purpose a favorable temperature coefficient is more 
important than field strength. In a torsion balanced magnetometer the TC of 
the magnet and the TC of the torsion wire add to cause drift error.

Many thanks,

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Larry Cochrane <cochrane@..............>