In a message dated 03/06/01, blottobear@.......... writes:

> I am used to dealing with teraohms, femtowatts, and picoseconds in my long 
> and
> illustrious dealings with those magical electrons - but how did an analog 
> signal with <10hz or so of bandwidth get involved with those fleeting 
> 

       It is the bandwidth of the seismometer signal that we want to record...

> The antique seismos used a moving mirror and an INCOHERENT light source and 
> wrote on a rotating drum located in a small vault-not hundreds of feet 
> away! The trace on the film was 1-2 inches or so for a typical (M7-9) large 
> quake.
> 

Dear Dave,

       The antique seismometers used a large coil to generate a signal which 
was then input into a sensitive galvanometer. A mirror on the galvo coil 
reflected a beam of light. You could read that out with a CCD, but there is 
currently more interest in wide band instruments with direct readouts. A 
reluctance bridge or a LVDT do this very nicely, thank you. So do tell us 
just how you plan to set us free with CCD?!

       Regards,

       Chris Chapman
In a message dated 03/06/01, blottobear@.......... writes:



I am u
sed to dealing with teraohms, femtowatts, and picoseconds in my long 

and

illustrious dealings with those magical electrons - but how did an analog 

signal with <10hz or so of bandwidth get involved with those fleeting 

nanoseconds?



       It is the bandwidth of the seismometer signal that we want to record...



The an
tique seismos used a moving mirror and an INCOHERENT light source and 

wrote on a rotating drum located in a small vault-not hundreds of feet 

away! The trace on the film was 1-2 inches or so for a typical (M7-9) large 

quake.

Yea, I sing the praises of the CCD, for it will set you free!!



Dear Dave,



       The antique seismometers used a large coil to generate a signal which 

was then input into a sensitive galvanometer. A mirror on the galvo coil 

reflected a beam of light. You could read that out with a CCD, but there is 

currently more interest in wide band instruments with direct readouts. A 

reluctance bridge or a LVDT do this very nicely, thank you. So do tell us 

just how you plan to set us free with CCD?!



       Regards,



       Chris Chapman