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 10metres 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