PSN-L Email List Message
Subject: Re: OT: an alternative use for a geophone
From: Nicholas Ward nicholas.ward@.........
Date: Thu, 13 Jul 2006 17:57:35 +0100
this is all very useful info,
On 13 Jul 2006, at 14:42, ChrisAtUpw@....... wrote:
> In a message dated 13/07/06, nicholas.ward@......... writes:
>> Thanks for the info.
>> On 13 Jul 2006, at 10:10, james fisher wrote:
>> > Hi, a piezo disk will pick up the higher frequencies
>> > you are interested in. use a 100 gram weight on top of
>> > the piezo disk and bury in a 1' deep hole to isolate
>> > disc from direct sound pickup. Superglue a strong
>> > magnet to disk and stick on a iron rod driven into the
>> > ground. Insulate everything well. See past posts on
>> > piezo disks. They really work well for picking up
>> > seismic waves as well as sound waves.
> Hi Nicolas,
> =A0=A0=A0=A0=A0=A0 You will need FET input opamp TL071? to match the =
> impedance of the piezo disk.
> =A0=A0=A0=A0=A0=A0 Superglue will not last long; a modified two part =
> Holdtite ST3295 is much better. It is tough and doesn't crack.
> =A0=A0=A0=A0=A0=A0 Can you stick the head of a 3 mm brass bolt to the =
> the piezo disk and screw a 20 gm disk of brass on top? A high weight=20=
> like 100 gm is OK for very low frequency seismic signals, but it=20
> lowers the resonance of the disk to maybe 200 Hz.
> =A0=A0=A0=A0=A0=A0 Regards,
> =A0=A0=A0=A0=A0=A0 Chris Chapman
Public Seismic Network Mailing List (PSN-L)
[ Top ]
[ Back ]
[ Home Page ]