## PSN-L Email List Message

Subject: Re: Notes to UK--Nick
From: "Mauro Mariotti" mariotti@.........
Date: Thu, 2 Jan 2003 16:15:35 +0100

```Hi,
yes, I am gree.
The simple design of the lacoste suspension should be
considered instead of a simple vertical spring.
I experimented several solution and i what i learned
the Lacoste suspension is the easier and better solution

Anyway the interesting life of seismo-amateurs is the=20
ability to experiments many solutions...
so all the ideas are always welcome!

regards
Mauro
----- Original Message -----=20
From: Jack Ivey=20
To: psn-l@.................
Sent: Thursday, January 02, 2003 3:33 PM
Subject: RE: Notes to UK--Nick

Mauro,
I'm not sure it will be _very_ sensitive to axial movements.  =
Horizontal
movements of the magnet will not cause as much change in magnetic=20
flux linkage through the coil as vertical movements because of the =
geometry
of the coil and magnet.  For movement in one horizontal direction, the =
magnet
is moving parallel to the wires at the top of the coil.  For the other =
horizontal
direction, the magnet is moving parallel to the flux between it's =
poles.  In either
case any flux change through the coil is a second order effect due to =
curvature
of the coil and curvature of the magnet path.  For vertical movement =
the flux=20
change is a first order effect, proportional to displacement.  As a =
guess I=20
would expect the horizontal sensitivity to be 5x to 10x down from the =
vertical. =20

Jack
-----Original Message-----
From: Mauro Mariotti [mailto:mariotti@..........
Sent: Monday, December 30, 2002 2:01 PM
To: psn-l@..............
Subject: Re: Notes to UK--Nick

Hi all,
I suggest a different approach for homemade vertical sensors.
The sensor in the link you propose is VERY sensitive to axial =
movements
(horizontal movements)
if you give a look to=20

http://www.infoeq.it/doc02v_e.htm=20

and scroll the page until you reach:

Lacoste suspension sensor=20

you can see a good approach to a sensitive=20
long period seismometer.

There are also sofisticated tecniques to=20
have a virtually infinite response for that kind
of seismometer using a "zero length spring".

Mr Lacoste writed a lot of paper on it.
Chris Chapman is better documented on this point.
I hope to have the time to publish an abstract on these tecnmiques
but any clever mind can understand how the Lacoste suspension
is great and simple to build.

Regards
Mauro

----- Original Message -----=20
From: John & Jan Lahr=20
To: psn-l@.................
Sent: Monday, December 30, 2002 6:47 PM
Subject: Re: Notes to UK--Nick

I've scanned Jim's Short Period design plans and put a copy on my =
web site here:
http://jjlahr.com/science/psn/lehman/
This will save on postage and make the plans available to more =
people.  They
are a good example of how to document a seismic sensor design.

Happy New Year,
John

At 12:15 PM 12/28/2002, you wrote:

Nick--I do not need an e-mail address.  I only needed your =
mailing address to send the "Short Period" design plans.
The plans were mailed airmail  to U.K. 2 days before =
Christmas.
A good New Year to you and all the PSN group.
J. Lehman.

Hi,
yes, I am gree.
The simple design of the lacoste =
suspension should=20
be
considered instead of a simple vertical =

spring.
I experimented several solution and i =
what i=20
learned
the Lacoste suspension is the easier =
and better=20
solution

Anyway the interesting life of =
seismo-amateurs is=20
the
ability to experiments many=20
solutions...
so all the ideas are always =
welcome!

regards
Mauro

----- Original Message -----
From:=20
Jack =
Ivey
To: psn-l@..............
Sent: Thursday, January 02, =
2003 3:33=20
PM
Subject: RE: Notes to =
UK--Nick

Mauro,
I'm=20
not sure it will be _very_ sensitive to axial movements. =20
Horizontal
movements of the magnet will not cause as much change in =
magnetic=20

flux=20
linkage through the coil as vertical movements because of the =

geometry
of=20
the coil and magnet.  For movement in one horizontal =
direction,=20
the magnet
is moving parallel to the wires at the =
top of=20
the coil.  For the other=20
horizontal
direction, the magnet is moving parallel to =
the flux=20
between it's poles.  In =
either
case any flux change through the coil is a =
second=20
order effect due to curvature
of the coil and curvature of the magnet=20
path.  For vertical=20
movement the flux=20

change is a first order effect, =
proportional to=20
displacement.  As a=20
guess I=20

would expect =
the horizontal=20
sensitivity to be 5x to 10x down =
from the=20
vertical.

Jack

-----Original Message-----From: Mauro Mariotti=20
[mailto:mariotti@..........Sent: Monday, December 30, =
2002 2:01=20
PMTo: psn-l@..............Subject: Re: Notes =
to=20
UK--Nick
Hi all,
I suggest a different approach =
vertical sensors.
The sensor in the link you =
propose is VERY=20
sensitive to axial movements
(horizontal =
movements)

if you give a =
look to=20

http://www.infoeq.it/doc02v_e.=
htm=20

and scroll the page until you=20
reach:

Lacoste suspension =
sensor=20

you can see a good approach to a =
sensitive=20

long period =
seismometer.

There are also sofisticated =
tecniques to=20

have a virtually infinite =
response for that=20
kind
of seismometer using a "zero =
length=20
spring".

Mr Lacoste writed a lot of paper =
on=20
it.
Chris Chapman is better =
documented on this=20
point.
I hope to have the time to =
publish an=20
abstract on these tecnmiques
but any clever mind can =
understand how the=20
Lacoste suspension
is great and simple to =
build.

Regards
Mauro

----- Original Message ----- =

From:=20
John =
& Jan=20
Lahr
To: psn-l@.............. =

Sent: Monday, December 30, =
2002 6:47=20
PM
Subject: Re: Notes to =
UK--Nick
I've scanned Jim's Short Period design plans and =
put a copy=20
on my web site here:http://jjlahr.com/science/psn/lehman/This =
will=20
save on postage and make the plans available to more people.  =

Theyare a good example of how to document a seismic sensor=20
design.Happy New Year,JohnAt 12:15 PM=20
12/28/2002, you wrote:
Nick--I do not=20
to send=20
the "Short Period" design plans.   The=20
plans were mailed airmail  to U.K. 2 days before=20
Christmas.   A good New Year =
to you=20
and all the PSN group.          &nbs=
p;            =
;      =20
J.=20
Lehman.=

```