[time-nuts] line frequency website

Hal Murray hmurray at megapathdsl.net
Fri Dec 30 20:07:32 EST 2011

> Well, I design systems that we send out all over the world. I have various
> spec numbers that indicate some rather optimistic tolerance. For example, I
> have measured actual outlets in the US at 70VAC and 142VAC, which is well
> outside the published tolerances. I get a lot of flack from management when
> I try to use those numbers as operational limits instead of the utility
> published ones. Some empirical evidence from a third party would help a lot.

70 and 142 seem more than a bit unreasonable.  How long did they stay at that 

I like Jim's suggestion of asking the guys who are collecting the data.


I've been using my UPS to monitor line voltage.  It's got commands to read 
the min/max input voltage since the last time you asked.

My software writes a line to the log file every 5 minutes or more often if 
the line voltage changes by more than 2 V.  It runs about 30K per day.

Mostly, things are boring: 120-125 V.  Occasionally I see a glitch.

I should write some code to scan the old files and collect statistics.

These are my opinions, not necessarily my employer's.  I hate spam.

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