Edward Ianni 
To: psnlist 
Sent: Mon, 17 Sep 2012 0:53
Subject: Old hobby resurgence

Hi all:         =20
I have two very old seismometers and I would like to extend their "periods"=
, electronically and EXTERNALLY if that is possible. I tried this a long ti=
me ago but I am not heavy into electronics and could not come up with the r=
ight values for some of the circuits that I looked at. The two Seismometers=
 are a Kinemetric SH1 "Intermediate"(about 5 second period), and a Sprengne=
ther (square box type) with a 1.5 second period. Is it possible to do this =
easily and is there a circuit somewhere with relatively simple instructions=
 for calculating component values? Thank You.  Ed.

Hi Ed,=20
    The short answer is Yes !=20
    You can extend the period of a seismometer electronically by about x10 =
with two stages of the parallel Robert's circuit, or you can use the simple=
r serial type used in the AS-1. So the Sprengnether could easily go out to =
15 seconds and bring in the surface waves fairly respectably. I suggest tha=
t you extend the SH1 only to about 25/30 seconds and this is a bit more dif=
ficult since you may have to suppress 1/f noise. You have the problem with =
requiring a 1/f^2 amplifier characteristic and this gain has to go to perio=
ds beyond what you require and the excess 1/f noise has to be filtered out.
Regards,=20
Chris Chapman

Edward Ianni <edwianni1@...........>

To: psnlist <psnlist@..............>

Sent: Mon, 17 Sep 2012 0:53

Subject: Old hobby resurgence



Hi all:
          

I have two very old seismometers and I would like to extend=20
their "periods", electronically and EXTERNALLY if that is possible. I=20
tried this a long time ago but I am not heavy into electronics and could=20
not come up with the right values for some of the circuits that I looked=20
at. The two Seismometers are a Kinemetric SH1 "Intermediate"(about 5=20
second period), and a Sprengnether (square box type) with a 1.5 second=20
period. Is it possible to do this easily and is there a circuit=20
somewhere with relatively simple instructions for calculating component=20
values? Thank You.  Ed.

 

Hi Ed, 

    The short answer is Yes ! 

    You can extend the period of a seismometer=
 electronically by about x10 with two stages of the parallel Robert's circu=
it, or you can use the simpler serial type used in the AS-1. So the Sprengn=
ether could easily go out to 15 seconds and bring in the surface waves fair=
ly respectably. I suggest that you extend the SH1 only to about 25/30 secon=
ds and this is a bit more difficult since you may have to suppress 1/f nois=
e. You have the problem with requiring a 1/f^2 amplifier characteristic and=
 this gain has to go to periods beyond what you require and the excess 1/f =
noise has to be filtered out.

Regards, 

Chris Chapman