From: Brett Nordgren
To: psnlist
Sent: Sat, 22 Sep 2012 0:39
Subject: Re: Old hobby resurgence
Hi Brett,=20
=20
The French school's seismometer system uses 4.5 Hz geophones out to 20 =
seconds period.=20
Lennartz use 2 Hz geophones for their 20 second period sensors and also=
give the reference to the Lippmann German patent - now expired. www.lennar=
tz-electronic.de But the output is low and you need a very low noise ampli=
fier and good filtering.
Regards,=20
Chris
=20
=20
From: Brett Nordgren <brett3nt@.............>
To: psnlist <psnlist@..............>
Sent: Sat, 22 Sep 2012 0:39
Subject: Re: Old hobby resurgence
Hi Brett,
The French school's seismometer system uses 4.5 Hz =
geophones out to 20 seconds period.
Lennartz use 2 Hz geophones for their 20 second per=
iod sensors and also give the reference to the Lippmann German pa=
tent - now expired. www.lennartz-electronic.de But the output is low and y=
ou need a very low noise amplifier and good filtering.