PSN-L Email List Message

Subject: Re: Magnetic Phono Cartridge as a Seismic Velocity sensor ?
From: ChrisAtUpw@.......
Date: Tue, 11 May 2010 19:03:25 EDT


 
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





In a message dated 11/05/2010, gmvoeth@........... writes:
Might=20 one use a magnetic phono cartridge as a seismic=20 sensor.
Hi Geoff,
 
    Phono cartridges are designed to do a very=20 different job. The motion is measured in thousanths of an inch, the freque= ncy is=20 the normal audio range, the output is in milli volts and they use a=20 ferromagnetic backing plate.
    For a vertical pendulum you need at least +/-= 0.5 mm=20 movement and for a garden-gate pendulum +/-10mm movement with good lineari= ty.=20 The frequency range is 10 Hz downwards, often to less than 0.05 Hz. These= are=20 not difficult to construct using inexpensive NdFeB magnets. For a vertical= =20 pendulum you can also use a Hall Effect magnetic sensor eg Allegro A1321.<= /DIV>
 
    Regards,
 
    Chris Chapman

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