In a message dated 19/09/05, kd6iwd@......... writes:

> Hi Chris, The meter has small bearings that typically are something like 
> synthetic ruby with a needle point pivot. I think that the very high intensity 
> magnetic
> field in a meter movement will make a good seismometer if coupled to a mass 
> to give it sensitivity. 

Hi Jim,

       They could make OK accelerometers for general purpose use, but they 
are very unlikely to be of much use as a seismometer. Only the torsion 
suspension types have the zero bearing friction necessary. Meter movements are often 
quite highly damped. 'Observable' seismic signals may be movements of just a few 
tens of nano metres, upwards. The ocean background signals with a period of 
about 6 sec, which are seen as quite large in seismic terms, are movements of 
only a few microns, typically about 2. Incidentally, moving coil meters are 
fairly expensive items in these days of LCD and LED displays.

       You can make OK cheap seismic sensors using the 41 / 50 mm dia piezo 
sounder disks and a weight, but you need a very high impedance low noise 
amplifier, maybe 100 M Ohms input.

       Regards,

       Chris Chapman
In a message=20=
dated 19/09/05, kd6iwd@......... writes:



Hi Chris, The meter has sma=
ll bearings that typically are something like synthetic ruby with a needle p=
oint pivot. I think that the very high intensity magnetic

field in a meter movement will make a good seismometer if coupled to a m=
ass to give it sensitivity. 




Hi Jim,



       They could make OK accelerometers f=
or general purpose use, but they are very unlikely to be of much use as a se=
ismometer. Only the torsion suspension types have the zero bearing friction=20=
necessary. Meter movements are often quite highly damped. 'Observable' seism=
ic signals may be movements of just a few tens of nano metres, upwards. The=20=
ocean background signals with a period of about 6 sec, which are seen as qui=
te large in seismic terms, are movements of only a few microns, typically ab=
out 2. Incidentally, moving coil meters are fairly expensive items in these=20=
days of LCD and LED displays.



       You can make OK cheap seismic senso=
rs using the 41 / 50 mm dia piezo sounder disks and a weight, but you need a=
 very high impedance low noise amplifier, maybe 100 M Ohms input.



       Regards,



       Chris Chapman