Hi Tim,
I've learned a lot from the responses to my original post. I had almost come
to the conclusion that a UPS wasn't going to do it for me before I started
this. Unfortunately, I can't afford to have a Generac running 24/7, so I was
hoping for alternatives. The idea of an inverter type system sounds good in
theory. The cost and complications were a concern. It's probably more of a
case of "fear of the unknown" than anything else. But, I was uncomfortable
with actually going out on a limb and putting one together. So, I ordered a
1KVA Sola constant voltage transformer. With any luck, it'll do enough that my
testing will settle down. If not, then I'm going to add a power-line monitor
of the type using a small transformer and a sound card. That would identify
times where tests weren't reliable. And that should be enough.
Thanks to everyone who posted. I certainly got my money's worth!
Bob
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From: Tim Shoppa <[email protected]>
To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
measurement <[email protected]>
Sent: Friday, July 8, 2016 1:27 PM
Subject: Re: [time-nuts] The home time-lab
Everyone else is talking as if these blips can be protected from, by having a
UPS supplying your precious lab equipment.
I strongly disagree.
What happens, is you have transformers, fluorescent ballasts, and motors (e.g.
HVAC blowers) in the vicinity of your lab equipment. Probably on a completely
different AC branch circuit, and not even necessarily in the same room but
maybe in an adjacent room or above or below your lab. With an inductive load,
every time there's a sudden power cut, a large back-EMF develops and then the
power suddenly comes back on and then there's a sudden large current as the
magnetic fields are built back up. It's these transient magnetic fields from
your non-lab equipment, that is what's disrupting your measurement.
If you now add a UPS in the vicinity of your lab equipment, and it of course
has a transformer in it, it will likely add to the disruption in a power glitch.
Of course things are a little different if you banish all AC power from a few
hundred feet of your lab and only run sustaining charging current for the DC
batteries developed in a far-away DC supply :-).
Tim N3QE
On Thu, Jul 7, 2016 at 8:44 PM, Bob Stewart <[email protected]> wrote:
I hope this isn't too far off topic, as this is having a big impact on my
testing.
I decided to run an A/B test on one of my GPSDOs: comparing the phase of the
two 10MHz output channels. In the middle of the night, there was a long series
of 35ns pops in the phase data. Strangely enough, there was nothing in the
data collected directly from the unit involved. The preceding two days we had
had a number of switching transients where the lights blinked but nothing shut
down. So, putting one and one together, I suspect that a fair percentage of
the strange results I've been getting has been power-grid related.
So, what to do? I've been looking at UPS devices, and I don't even understand
enough to waste my money on a bad one. The two big questions seem to be
"on-line" and "sine wave". Make that three: can I trust the mfgs claims? Is
there something affordable that could run a pair of 5370s and maybe another 50W
worth of DUTs for up to an hour or two and not be prey to power-line
transients? Or would it be more cost effective to somehow monitor the power
line for spikes or phase jumps and blow off tests or cut out the offending
data? From time to time we get a thread on power-line nuts. Should I have
been paying more attention?
Bob - AE6RV
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