PSN-L Email List Message

Subject: RE: 3 ebay auctions
From: "Doug Crice" dcrice@............
Date: Sun, 21 Mar 2004 13:58:00 -0800

The seismoscope on ebay is an
instrument designed to record acceleration levels from earthquakes.  It =
a comparatively low-cost way to measure local vibrations from =
earthquakes to
determine ground and structural amplification factors in an earthquake.

The recording medium was a piece of glass which was smoked with a =
candle. A
needle would scribe the glass as the pendulum oscillated horizontally. =
the bottom of the pendulum is a semi-spherical aluminum disk, which hung
close to a magnet.  As the pendulum swings, eddy currents are induced in =
disk which damp the motion of the pendulum, giving the unit reasonably =
frequency response over the bandwidth of interest.

Because of their low cost, you could install a large number of these =
a site of interest to supplement the more advanced and more expensive
accelerographs (strong-motion seismographs). In one of the early bids =
for a
large number of these, I believe Kinemetrics got the bid because they =
a steam table pot just the right size and cheap for the cover. The =
window in
the cover lets you inspect the glass without opening the lid.

A clever hobbyist might be able to supplement the watch glass with a
position transducer to make a recording instrument for strong =

Doug Crice
12996 Somerset Drive                phone 1-530-274-4445
Grass Valley,  CA  95945  USA    fax 1-530-274-4446

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
Sent: Sunday, March 21, 2004 7:09 AM
To: psn mail
Subject: 3 ebay auctions

~ INTERESTING GERMAN SEISMOGRAPH ? ~ 	 Item number: 2233608755 =09
   ends Mar. 30
A fascinating mechanism!  My guess is that it is not a seismograph but=20
What is it??
Soiltest Engineering Seismograph MD-3 	 Item number: 3282498791
   ends Mar. 27
SEISMOSCOPE U-17 - Dominion OBSERVATORY, VICTORIA BC 	 Item number:=20
3282408861 =09
   ends Mar. 27
   I have no idea that this is--pictures are poor.


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