[time-nuts] The home time-lab

David davidwhess at gmail.com
Fri Jul 8 04:28:40 EDT 2016


On Thu, 7 Jul 2016 21:31:58 -0400, you wrote:

>If you decide to go the UPS route, don’t bother with anything that does not produce a sine wave 
>output. Modern power factor corrected stuff is a lot happier with sine waves than with weird looking
>semi-square wave stuff.

Active power factor correction should not care about input wave shape
but it would not surprise me of there were poor designs which have
issues.  What happens with these?

>By far the most expensive gear is the stuff that runs full time. You take the AC line and convert it to DC.
>That plus a battery supply the DC to sine wave converter. Everything downstream runs off of the DC to 
>sine wave converter all the time. Since it always supplies the gear, it needs to be big enough to supply
>whatever surge the gear requires.  That tends to make them a bit large 


I have a couple of used but refurbished online UPSes and they work
great.  I picked them up from either www.upsforless.com or
www.refurbups.com.  This is the only deal I see at the moment but I do
not know how suitable it would be and it is more than I paid although
about twice as powerful:

http://www.upsforless.com/apcsurta1500xlref.aspx

>None of the UPS systems take care of all issues. There are things like RFI and ground isolation that 
>still *could* be an issue. To get into the next layer of that onion you go with stuff like faraday cages and
>fairly big filters. 

Neutral and/or common mode filtering or the lack of it may be the
biggest problem.  A couple of years ago there was a change in UL
regulations for UPSes concerning how the neutral output is wired which
may have affected this:

http://www.apc.com/us/en/faqs/FA156549/


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