Horizontal vs. Vertical Geophones

[GeraldP]

Hi O.S.O.P.,

I just watched  https://www.youtube.com/watch?v=BR72uzdoWhM  and saw your video about the inside of a geophone.  It was interesting.  I've always been curious about how things work.  I assume tit was a vertical geophone, since they are the most common.

Being curious, I wonder what the "mechanical" difference between the Vertical and Horizontal geophones?  

I can see that the one you cut open had very close tolerances.  I can imagine that a vertical up and down motion could be held reasonably "tight," and any wobble to a minimum; especially if kept level. 

However, the horizontal coils and magnetic element might "drag" under the influence of gravity.  I was wondering how that was compensated for mechanically?

Put on you thinking cap!  (Smile)

Jerry (RFAE6)

[chris...@aol.com]

Hi Jerry, 

    The OSOP youtube description of a geophone seems to me to be misleading. There is a central 

cylindrical magnet surrounded by a soft iron tube, suitably electroplated to prevent corrosion. 

Between these, a thin Copper tube carrying two coils, one for each end of the magnet, is 

suspended by semi flat spiral springs. The Copper tube + windings form the moving mass and the 

spiral springs at opposite ends of the geophone also carry the voltage output. It is the 'pre set' of 

these end springs which determine whether it is a horizontal (no axial force) or a vertical (supporting 

the mass of the armature) geophone. 

    Regards, 

    Chris

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[GeraldP]

Thanks Chris.  I didn't think it was levitation. (smile)

Yes, I can see that the function of the springs could be the difference.