Dear Chris:

Thank you for all your suggestions, and we'll try the ones we haven't
tried already. However, we may not have been clear about our two-fold
objective. First, it is to build (or better yet, provide plans to
build) simple, transparent, and robust educational sensors for kids of
all ages. This was the background from where Doug's questions were
raised to the psn list. Second, we are adamant about providing "open
source" materials.
This means all our plans are posted online, for people to use and improve.
It is my understanding you have not had the pleasure to run a
Slinky Seismometer (yet). We encourage you to build one -- it does not
take but a few hours -- and see how your presumed improvements work
out!  But keep in mind, we gladly sacrifice performance for any of the
qualities mentioned above. Even so, dozens of slinkies around the
globe -- some on carpet on the second floor of busy school libraries
-- detect earthquakes with great frequency (as in number of events: we
really don't mind if the dominant f is 1.3, 1 or 0.7 Hz). To suggest we
don't detect teleseismic events does not make sense, as you can see
from the long list of processed EQs around the globe posted on our site.
The frequency response is not flat over the maximum range, and we
don't mind! The
slinky seismometer may not be a satisfactory tool to the well-educated
community of PSNers, but sure is nice for kids who know very
little about earth science. Distinctions between seismometers,
seismographs, and geophones are here-nor-there for our project. We
also take small (variable) filter delays in stride. Vertical
temperature gradients in cases, as well as daily temperature variations, we
also gladly wipe under the same rug our sensors are sitting on! Now
for some more detailed responses:

We do have the Manuals you spoke of and that=92s very useful
information. We especially like the pdf of the SEP.  Ted got it as
soon as it was published. Very nice. To keep this short we are not
going to try to cover all your observations, but assure you we
understand them, and we will look at each and every one.

About the interface between sensor and computer:
We set out to create a low-cost daq that was easy to build and use and that=
 had
 an acceptable dynamic range and we think we succeeded.  We don't know that=
 any
improvements to the signal path would have advanced our primary goal
(simple, effective instruments in schools), but it likely would have
increased the cost and
complexity.

We do wish to cover the damper issue as that seems to be a reoccurring
comment.   Mainly from people who do not use the sensor.
The fact is the present instructions and position of the damper, works
very well.  We found it unnecessary to define it further, for three
reasons.

1.  It works, we have recorded hundreds if not thousands of EQ over
the seven years, with no indication there is a problem.

2.  Ted created a bench test, where he displaces the spring=92s mass
10mm, released the mass, the spring moved passed zero, it=92s resting
position, continued 0.5mm, back to zero and stopped.  To make sure, he
places a scale and a needle and a magnifying glass inside to view the
action.

3. The end user is free, but not encouraged, to add a second ring
magnet to the damper, if they feel it is under damped.   I don=92t know
why anyone would do this, but the design allows you to add as many as
you like.  Explore!

We do understand all the thermo disadvantages of a slinky spring and
the period limitation, as well, but the Slinky VIII works very well in
spite of them, and allows students to build it, set it up, and
record lots of events.  As is, the device will record earthquakes
near and far and it is simple enough for a 12-yr old to build and operate:
Jacob's quest is documented on our site.

Ted normally has two or more of these verticals running in his shop, to
carefully compare modifications, and we look forward to trying your suggest=
ions
with hopes we can introduce Slinky IX, given the boundary conditions
defined by our
objectives stated at the beginning of this message.

kasper, ted and martin
__________________________________________________________

Public Seismic Network Mailing List (PSNLIST)

To leave this list email PSNLIST-REQUEST@.............. with 
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.