I have previously posted this reply (to different questioners) on the ARSCLIB and the SAA mailing lists. I have done surveys like this and bought a meter. With a three-axis meter no particular concerns are necessary. In general, I found the levels in most situations to be below what will damage tape. In the old days, CRT monitors were about the most sensitive devices we had. 10 mG or less for crt monitors was the goal. This question was asked in a different form (what is the level that puts tapes at risk) on the ARSCLIB list. I will repost my reply here: The reference I have used for years is: www.mrltapes.com/field-strength-for-partial-erasure.pdf I bought a one-piece 3-axis meter for about $150 from these folks about a decade and a half ago. http://www.lessemf.com/gauss.html This looks like a good choice at $150 XYZ Axis EMF Tester (Cat. #A194) However, the unit I have I think goes out to higher harmonics which might be interesting with large three-phase power installations, so another choice on the same page for $269, but it may be overly sensitive and not be able to measure higher strength fields discussed in the paper. 3-Axis Backlight Gaussmeter (Cat. #A107) For $300 it looks as if this might be closest to what I had and found most useful. Switchable 1:3 Axis Gaussmeter (Cat. #A153) Though for $200 you can get this: Datalogging 3-Axis Gaussmeter w/ PC (Cat. #A494) Cheers, Richard On 8/15/2016 12:25 PM, Ruede, Laura wrote: > Hi - > > The Texas Christian University Library is looking to move some archival magnetic sound and video recordings to new areas in the library and our off-site facility not far away. Before we do this, however, we need to be sure that electro-magnetic fields in those areas are not above tolerance, in order not to damage the recordings. I have some information on acceptable levels for this sort of material, but we don't have a gauss meter or other measuring device, and no one on staff has the expertise to wield such a thing. TCU Physical Plant doesn't have a device or the necessary expertise either. > > I have the idea that a gauss meter wouldn't be too expense to purchase, so we could do that if needed. I thought I'd ask whether there's anyone reasonably local who would be able to help us further, or if not, if anyone can refer me elsewhere. Thanks very much - > > > Laura J. Ruede, MLS > Van Cliburn Archivist > TCU Box 298400 > Fort Worth, TX 76129 > 817-257-7774 > -- Richard L. Hess email: [log in to unmask] Aurora, Ontario, Canada 647 479 2800 http://www.richardhess.com/tape/contact.htm Quality tape transfers -- even from hard-to-play tapes.