Subject: RE: Lehman seismometer movement


Has anyone tried to see real-time boom=20
ovement by setting up a mirror and=20
aser pointer as an optical lever?
 set one up one time with little=20
esult, but I didn't try very hard.
There are drawings of such a thing for
hotocell position detection from
ome of the early Amateur Scientist=20
rticles.
Hi Jack,
    Work it out? You can easily detect a movement of 100 nano metres.
If you have a 50cm boom and mount a laser on it and your house is 10=20
metres long, you would get a spot movement of just 2 microns. OK, you=20
could use multiple reflections of a laser beam and get maybe 32 microns,
but this is still a very tiny spot movement.
    With differential large area Silicon photocells and an amplifier, =20
the noise level can be about 7 nano metres, so this is a practicable=20
measurement technique.
    Regards,
    Chris Chapman=20



<=
TT>





=
Subject: RE: Lehman seismometer movement





Has an=
yone tried to see real-time boom=20
movement by setting up a mirror and=20
laser pointer as an optical lever?
I set one up one time with little=20
result, but I didn't try very hard.

There are drawings of such a thing for
photocell position detection from
some of the early Amateur Scientist=20
articles.

Hi Jack,
=
    Work it out? You can easily detect a movement of 100 nan=
o metres.
If you have a 50cm boom and mount a laser on it and your house is 10 
metres long, =
you would get a spot movement of just 2 microns. OK, you 
=
could use multiple reflect=
ions of a laser beam and get maybe 32 microns,
but this is still a very tiny spot m=
ovement.
=
    With differential large area Silicon photocells and an amplifier,  
the noise le=
vel can be about 7 nano metres, so this is a practicable 
=
measurement technique.
    Regards,=
    Chri=
s Chapman