[time-nuts] The home time-lab

Charles Steinmetz csteinmetz at yandex.com
Fri Jul 8 18:37:01 EDT 2016

Tim wrote:

 > I strongly disagree.
> What happens, is you have transformers, fluorescent ballasts, and motors
> *  *  * in the vicinity of your lab equipment.  *  *  *  not even necessarily in the
> same room  *  *  *  every time there's a sudden power cut, a large back-EMF
> develops and then the power suddenly comes back on and then there's a
> sudden large current as the magnetic fields are built back up. It's these
> transient magnetic fields from your non-lab equipment, that is what's
> disrupting your measurement.
> If you now add a UPS in the vicinity of your lab equipment, and it of
> course has a transformer in it, it will likely add to the disruption in a
> power glitch.

Both theory and experience show that this is not the usual case.  (Note 
that certain grounding problems can make it appear initially as if there 
are magnetic-field problems, but closer analysis reveals that incorrect 
grounding is the actual cause.)

The magnetic fields you describe are very localized and diminish rapidly 
as you move away from the source.  The shielding normally provided by a 
metal (or even metallized plastic) housing is plenty to prevent most 
problems of this nature, and moving extremely sensitive circuits a few 
inches to a few feet is generally enough to resolve any remaining issues.

If magnetic fields were the main problem, it would be impossible to 
build and use stereo systems, televisions, telephones, and any sort of 
electronic device that monitors or controls anything. Every time the 
refrigerator started up, there would be a huge BANG through the stereo, 
TV, radio receivers, and telephone, and all of your shop electronics 
would go crazy.

The usual problem is glitches on the on-site AC mains supply, and 
properly designed and installed on-line UPS systems do a very fine job 
of cleaning that up.

Best regards,


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