Subject: C-Spring Sensor - 5/6 Second Period
Has anyone tried this one? A vertical with a 5 to 6 second period using two=
hacksaw blades. Would like to hear opinions as to whether this is a worth-=
while build.
=20
http://www.fairpoint.net/~sparksite/CSpring%20Printer.html
=20
Hi Richard,
=20
This is an old design. Never use oil damping. It is non linear both wit=
h period and with amplitude. It is hideously temperature sensitive and it i=
s not easy to adjust..
=20
There is a design for a magnetic damper for a vertical seismometer at w=
ww.jclahr.com/science/psn/chapman/as1%20damping/index.html Mount the 1/16" =
thick copper damping blade on the arm and put the quad damping magnet block=
on the base. You can use soft Aluminum sheet for the blade - if you can bu=
y it - NOT hard or alloy sheet - but copper is better, since it is not sign=
ificantly diamagnetic.
=20
Buy fully hardened hacksaw blades.The ordinary ones have a hardened edg=
e, but with a softer blade. Grind off both the teeth and the wavy bends on =
the base, otherwise you get cracks developing quite rapidly when the blade =
is stressed.
DON'T mount a magnet on a seismometer arm. It picks up noise from the =
Earth's magnetic field, current surges in the house wiring, the movement o=
f large vehicles, etc. Mount the pickup coil on the arm and use a shielded =
quad NdFeB magnet block, or use an optical position detector.
The response can easily be extended to over 20 seconds using Robert's c=
ircuit for extending the period of geophones. You can get a x10 period exte=
nsion before running into sensor / amplifier noise, but it does mean that y=
ou have to build your own specialised amplifier - not too difficult to do u=
sing stripboard? See www.jclahr.com/science/psn/epics/roberts/index.html=20
Do look through the articles on the jclahr website.
Regards,
Chris Chapman
=
Subject: C-Spring Sensor - 5/6 Second Period
Has anyone tried this one? A vertical with a 5 to 6 second period usin=
g two hacksaw blades. Would like to hear opinions as to whether this is a w=
orth-while build.
Hi Richard,
This is an old design. Never use oil damping. It is=
non linear both with period and with amplitude. It is hideously temperatur=
e sensitive and it is not easy to adjust..
There is a design for a magnetic damper for a verti=
cal seismometer at www.jclahr.com/science/psn/chapman/as1%20damping/ind=
ex.html Mount the 1/16" thick copper damping blade on the arm and put t=
he quad damping magnet block on the base. You can use soft Aluminum sheet f=
or the blade - if you can buy it - NOT hard or alloy sheet - but copper is =
better, since it is not significantly diamagnetic.
Buy fully hardened hacksaw blades.The ordinary ones=
have a hardened edge, but with a softer blade. Grind off both the tee=
th and the wavy bends on the base, otherwise you get cracks devel=
oping quite rapidly when the blade is stressed.
DON'T mount a magnet on a seismometer ar=
m. It picks up noise from the Earth's magnetic field, current surges =
in the house wiring, the movement of large vehicles, etc. Mount the pickup =
coil on the arm and use a shielded quad NdFeB magnet block, or use an optic=
al position detector.
The response can easily be extended to over 20 seco=
nds using Robert's circuit for extending the period of geophones. You can g=
et a x10 period extension before running into sensor / amplifier noise, but=
it does mean that you have to build your own specialised amplifier - not t=
oo difficult to do using stripboard? See www.jclahr.com/science/psn/epics/=
roberts/index.html
Do look through the articles on the jclahr website.=
Regards,
Chris Chapman