[time-nuts] time-nuts Digest, Vol 69, Issue 31

Dave Baxter dave at uk-ar.co.uk
Wed Apr 14 04:00:55 EDT 2010

> Message: 4
> From: SAIDJACK at aol.com
> That is a big concern of ours of course!
> It's a massive voice coil in the shaker..
> bye,
> Said
> In a message dated 4/13/2010 11:20:16 Pacific Daylight Time, 
> neil at gruending.net writes:
> True  enough, but don't forget that a shaker table is a big 
> moving electromagnet  right next to the device under test. I 
> would think that the shaker's field  would dominate any such 
> errors, especially for larger tables running in  random 
> vibration or pulse  modes.

I think you'll find that any stray fields from industrial shaker
systems, are often from the connecting leads, especialy if not correctly
positioned and layed out.  The internal static and dynamic magnetic
fields are "Very" well contained.

My example with the small speaker though, you could expect some field
leakage.  However, the speakers from old PC monitors (CRT types) are
often very well shielded themselves, static and dynamic.

The "injection stick" is a good method of moving such field away
(inverse square law again) from the EUT.   Of course, if the field is
the problem, you'll see disturbance effects, long before the mechanical
connection is made.

Play and lean.


Dave B.

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