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 for a homemade design. 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 beconsidered instead of a simple vertical = spring.I experimented several solution and i = what i=20 learnedthe Lacoste suspension is the easier = and better=20 solutionfor a homemade design.Anyway the interesting life of = seismo-amateurs is=20 theability to experiments many=20 solutions...so all the ideas are always = welcome!regardsMauro=----- Original Message -----From:=20 Jack = IveySent: Thursday, January 02, = 2003 3:33=20 PMSubject: RE: Notes to = UK--NickMauro,I'm=20 not sure it will be _very_ sensitive to axial movements. =20 Horizontalmovements of the magnet will not cause as much change in = magnetic=20flux=20 linkage through the coil as vertical movements because of the = geometryof=20 the coil and magnet. For movement in one horizontal = direction,=20 the magnetis moving parallel to the wires at the = top of=20 the coil. For the other=20 horizontaldirection, the magnet is moving parallel to = the flux=20 between it's poles. In = eithercase any flux change through the coil is a = second=20 order effect due to curvatureof the coil and curvature of the magnet=20 path. For vertical=20 movement the flux=20change is a first order effect, = proportional to=20 displacement. As a=20 guess I=20would 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 PM
To: psn-l@..............
Subject: Re: Notes = to=20 UK--NickHi all,I suggest a different approach = for homemade=20 vertical sensors.The sensor in the link you = propose is VERY=20 sensitive to axial movements(horizontal = movements)http://www.infoeq.it/doc02v_e.= htm=20if you give a = look to=20and scroll the page until you=20 reach:Lacoste suspension = sensor=20you can see a good approach to a = sensitive=20long period = seismometer.There are also sofisticated = tecniques to=20have a virtually infinite = response for that=20 kindof 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 tecnmiquesbut any clever mind can = understand how the=20 Lacoste suspensionis great and simple to = build.RegardsMauro----- Original Message ----- =From:=20 John = & Jan=20 LahrTo: psn-l@.............. =Sent: Monday, December 30, = 2002 6:47=20 PMSubject: Re: Notes to = UK--NickI'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. = They
are a good example of how to document a seismic sensor=20 design.
Happy New Year,
John
At 12:15 PM=20 12/28/2002, you wrote:
Nick--I do not=20 need an e-mail address. I only needed your mailing address = 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.