wrote:
> Hello PSN Folks;
>
> Has anyone ever used a spring
> to take up most the mass weight then
> maybe apply an ounce or less levitation
> magnetically to set with electronics
> the free period within a geophone.
>
> Id think you would pump a current limited signal
> into the geophone and use some kind of
> feedback circuit that might set
> the free period. I am looking only
> for a free period in the 3 to 4 second
> range.
>
> If you take up the small weight with your hand
> it seems you can move the hand up and down
> at whatever period and the system will
> not oppose what you are doing ??
>
> Comments welcome.
>
> Regards
> geoff
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Hi Geoff,
I tried a brief test on my steel "HD pivot vertical" which is basically like a "traditional"
spring vertical; where opposing/repelling magnets were installed. The normal period
of it was 2 seconds without magnets.
I put a 1" ring magnet on the end of the test steel mass (facing to the front and centered).
I put a larger disc (same, or repelling pole) magnet about 3" in front of it at about the
same height.
The steel base does interfere abit of course, as the magnet on the mass will have
a attraction to the steel base underneath. Here, I added a smaller opposing magnet
(you could call it a "bias" magnet), alittle in front and directly onto the steel base
below the mass with its magnet.
It was easy to move the magnet out front, to see where it either shortens
the natural period (easy to do); or, lengthen the period. It takes abit of trial and
error, but within afew minutes I could see a period of ~ 5 seconds. I'am guessing
that with a better tweaking position arrangement, its quite possible to see
even a longer period.
The harmonic motion did hesitate abit on the downstroke peak. I'd expect the
"bias" magnet would need tweaking there too....or, of course just use a
aluminum base.
The thought does occur, that the magnets could well limit or force the centering
of the mass or perhaps help limit some of the spring temperature drift somewhat.
Of course, trying to "somehow" still use a pickup coil on such, is likely out of
the question. One would have to use a different sensor.
Take care, Meredith
On Dec 5, 2007 8:41 PM, Geoff <
gmvoeth@...........> wrote:
Hello PSN Folks;
Has anyone ever used a spring
to take up most the mass weight then
maybe apply an ounce or less levitation
magnetically to set with electronics
the free period within a geophone.
Id think you would pump a current limited signal
into the geophone and use some kind of
feedback circuit that might set
the free period. I am looking only
for a free period in the 3 to 4 second
range.
If you take up the small weight with your hand
it seems you can move the hand up and down
at whatever period and the system will
not oppose what you are doing ??
Comments welcome.
Regards
geoff
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To leave this list email
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