Back to the light thingy,
Given A Mass and Spring:
It Seems To Me You might get
X1000 magnification of motion
by putting a light source with a small radius
fixed to a stationary location connected to the mass and then
like 50 to 100 feet more away sensing
the lights motion.
It all has to do with the fact that as the radius increases
so does the velocity at the perimeter.
And if you can bounce the light beam between two mirrors
It might travel 100 feet in a relatively small space.
It will not matter that light is only 400 to 800 angstrums ??(not sure of spelling)
because one nano meter at the source becomes one micro meter
at its destination, and, like light has no mass ??

Have you ever seen such a mechanically amplified sensor before ?



----- Original Message ----- 
From: 
To: 
Sent: Tuesday, May 11, 2010 4:03 PM
Subject: Re: Magnetic Phono Cartridge as a Seismic Velocity sensor ?


> 
> In a message dated 11/05/2010, gmvoeth@........... writes:
> 
> Might  one use a magnetic phono cartridge as a seismic  sensor.
> 
> 
> 
> Hi Geoff,
> 
>    Phono cartridges are designed to do a very  different job. The motion 
> is measured in thousanths of an inch, the frequency is  the normal audio 
> range, the output is in milli volts and they use a  ferromagnetic backing plate.
>    For a vertical pendulum you need at least +/-0.5 mm  movement and for a 
> garden-gate pendulum +/-10mm movement with good linearity.  The frequency 
> range is 10 Hz downwards, often to less than 0.05 Hz. These are  not 
> difficult to construct using inexpensive NdFeB magnets. For a vertical  pendulum you 
> can also use a Hall Effect magnetic sensor eg Allegro A1321.
> 
>    Regards,
> 
>    Chris Chapman
>
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