[time-nuts] Re: Another reason to monitor line frequency :) - My AC measurement project & question

[willl will]

On 1/21/22 7:00 PM, Robert LaJeunesse wrote:
> Stick with the transformer. The use of a capacitive divider is predicated
on the line waveform always being a sine wave. Dream on! All it takes is
one good spike down the line, maybe only 20-30V amplitude, and your
capacitive divider passes it right on to that ADC that has a much lower
(3.3V?) limit. Guess what goes poof?
>
> Bob L.

I am concerned about this even with the transformer, so I've added Ti's TVS
chips & hookup the transformer after my UPS surge protection plug in the
previous project.
Definitely need to step up the protection level using an NTC resistor or
something like that to handle mains voltage directly..... Or offload the
concern to a surge protection plug.

Will


Lux, Jim <jim at luxfamily.com> æ–¼ 2022å¹´1月22æ—¥ 週å
­ 上午9:46寫道：

> On 1/22/22 8:21 AM, Bob kb8tq wrote:
> > Hi
> >
> > None of these transformers are designed for audio use. The same is true
> > of the various inductors and capacitors mounted up on power poles to try
> > to phase correct the distribution process. Pretty much all of them are
> “out
> > in the wild” and thus exposed to fairly large temperature swings.
> >
> > All of that suggests that the typical power distribution line is pretty
> narrow
> > band / low pass. Indeed back in the day, that’s what we found when
> measuring
> > this and that.
> >
> > I’d vote for sticking with the transformer.
> >
> > Bob
> >
>
> As always, there's a standard for that..
> ANSI/IEEE C62.41-2002, “Guide on the Surge Environment in Low-Voltage
> (1,000 V and less) AC Power Circuits.”
> (which is inactivated as of 2021, but reserved, I think there's a
> replacement coming out)
>
> This is probably a Category A or B location
>
>
> https://www.eaton.com/content/dam/eaton/products/backup-power-ups-surge-it-power-distribution/complete-home-surge-protection/eaton-eatons-guide-surge-suppression-application-notes-sa01005003e-ca.pdf
>
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