You gentlemen are so much advanced and more educate than I that I almost 
hesitate to ask this question.  A lot of your discussions, especially math 
and physics, go right over my head.  However, here goes:

I have always wondered why a mass is needed.  Why could not the coil itself 
be used as the mass on a pendulum seismometer?

If  I understand what I have read in my books (questionable), the size and 
weight of a mass has nothing to do with the period.  Futhermore, I believe 
the length of the pendulum and supporting spring or wire on a horizontal or 
vertical sensor matters more for obtaining the wanted period, excluding 
friction loses etc.  The coil is only the desired method of detecting 
movement.

Regards,
Jerry Payton








You gentlemen are so much advanced and more educate than I that I =
almost=20
hesitate to ask this question.  A lot of your discussions, =
especially math=20
and physics, go right over my head.  However, here goes:
 
I have always wondered why a mass is needed.  Why could =
not the=20
coil itself  be used as the mass on a pendulum seismometer?  =

 
If  I understand what I have read in my books (questionable), =
the size=20
and weight of a mass has nothing to do with the period.  =
Futhermore, I=20
believe the length of the pendulum and supporting spring or wire on a =
horizontal=20
or vertical sensor matters more for obtaining the wanted period, =
excluding=20
friction loses etc.  The coil is only the desired method =
of=20
detecting movement. 
 
Regards,
Jerry Payton