PSN-L Email List Message

Subject: Re: Re[2]: noisy power supply
From: Mariotti Mauro mariottim@......
Date: Sun, 09 Jul 2000 09:06:09 +0200

Be careful when you choice a point to wire the ground.
If you use a water pipe, for example, you may risk, if accidentally
a 110V power supply line (or here in Europe 220V power supply line)
touch for a moment the ground wire you will find one phase of the
AC current onto your water pipe system!
And if your electric plant it is not protected with a differential
interruptor it could be the cause of the DEAD os someone.
I think is better to provide a GOOD ground discharge point with
planting a copper rod of 1.5 .. 2 mt directly in the ground.
If a technician do this it's better.
About noise I think this is the main problem of amateur seismologist,
due the equipments are very sensitive to electromagnetic fields.
Pay attention with ground loops, shielded cables, and circuitry metal cases.
In some occasions metal cases induced more disturbances rather than the
plastic ones due ground loops caused by metal case to copper pour of
the pcb looped again on the metal case and so on with shielded cables
that link one board to the next.
One counsil to apply is:
1. Place your horizontal sensors in stable position rollin them to one
side, the pendulum will set at right or left without oscillate.
2. Lock the mass of your vertical sensor.
3. Now set you gain amplfier to the maximum.
4. watch the chart of SDR of other acquisition prgram
5. if you see the trace moving up and down slowly or quickly be sure
that what you se it is'nt a seismic signal.
6. So you can start to make experiments and reduce this noise that
surely is electromagnetic noise, 
7. after this you can set up again your sensors and you will see
   the most clean trace you never see before

Mauro Mariotti

At 14.34 07/07/2000 -0700, you wrote:
>Angel --
>Another thing for your shopping list might be copper strap -- 3 or 4" wide.
> It is available in some amateur radio or marine radio shops, sometimes
>marine hardware stores.  It's used to provide a good ground for radios on
>fiberglass boats, but makes good grounding strap in any case.
>Use it to connect the chassis of various parts of your system together, and
>to whatever earth connections are the best -- metal water pipes, antenna
>tower bases, ground rods, etc.
>At 07:32 PM 7/7/2000 -0500, you wrote:
>>I'm going to Seattle latter this month and various ferrite cores along
>with some small
>>inductors and some Radio Shack things are on the shopping list.  The
>>only electronic parts I can get are those used to repair TV's
>>and VCR's, :-)  it's real limiting some times.
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Larry Cochrane <cochrane@..............>