[time-nuts] The difficulty of low noise measurements

[Magnus Danielson]

Hi,

On 2020-01-12 17:08, Poul-Henning Kamp wrote:
> --------
> 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.
Sure. I have not cared myself so far, because I have so far not really
considered my lab being "in production" enough to care about such
details. I will get there.
>
> I tell my customers to dimension UPS batteries for at least one hour.
Which covers most issues on power-grid anyway.
>
> 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.
>
The folks I know actually test their diesels auto-start regularly. They
also check condition of batteries and how much diesel is left. Yes, some
people do test their diesel engines regularly, but fail to check how
much diesel remains.

Now, I think the UPS things is starting to be a little too off topic, so
let's not continue this part of the thread much longer.

Cheers,
Magnus