[time-nuts] The difficulty of low noise measurements

[Poul-Henning Kamp]

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In message <95f82880-6cec-1885-c59e-046ab7a79d0f at rubidium.se>, Magnus Danielson writes:

>>> I have a ham friend that is fairly well into batteries as he needs to
>>> for his telecom installations.
>> LVDC people are much better at this than UPS people, the latter often
>> think that batteries only need to last "until the diesel kicks in"
>> and that is a very different application.
>
>If you have a diesel, then the UPS is just a bridge. If you don't it is
>the bridge until the power grid is back.

Indeed, but the batteries still matter.

UPS people tend to fail to explain to their customers that batteries
dimensioned for only 10 or 20 minutes will not last many such cycles.

If you do not test your UPS on a regular basis, that may be a valid
tradeoff, but if you test it, as you should, once per month, you
will kill such underdimensioned batteries in three years.

I tell my customers to dimension UPS batteries for at least one hour.

It is be cheaper in batteries in the long run, at it gives their
staff a fighting chance if the diesel does not auto-start.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.