Hi all,

Of course the restoring moment which is developed by the hinge in any
seismometer is important, but it fades in importance compared to the
restoring moment which is introduced by the damping method.

A hydraulic damper will use some sort of piston or blade.  Motion of the
piston or blade through the liquid will involve setting some of the liquid
into motion.  To set anything into motion requires overcoming inertia, which
will make the initial piston or blade movement "sticky".  I think this can
be minimized by using a liquid with higher viscosity at the same time as the
minimum blade or piston size is used.

I am less familiar with magnetic damping so I hesitate to comment.  The
hysteresis of metal will be important.  Perhaps someone could comment on
magnetic damping.

Roger




__________________________________________________________

Public Seismic Network Mailing List (PSN-L)