Hi  Bob,


I've added the message below to the information that I'm gathering for
the Colorado 

School of Mines students who are working on designing an inexpensive
sensor.  I hope

that is OK with you.


See the link under AD's on this page:

http://www.jjlahr.com/science/psn/epics/links.html


Cheers,

John


At 12:45 AM 9/6/2002 -0400, you wrote:

Hi Ed,


  I use the DI-194RS and the DI-154RS for seismic recording. 
The DI-154 is preferable over the DI-194 because it has 12-bit A/D
conversion, but at the same time, it costs $150 compared to the $25 paid
for the RS-194.  It will work with your setup, I believe, but your
preamp should have a full scale range of +/- 10 volts in order to get all
of the dynamic range available from the Dataq starter kit.


  The Dataq unit samples at a fixed rate of 240 samples per second,
but records at any desired rate that is an integer divide of 240. 
All of the acquired data is input signal averaged, which improves
resolution, increases signal-to-noise ratio, attenuates aliasing, and
totally rejects 60 Hz and 120 Hz hum.  For example, I usually record
at 5 samples per second.  During the 0.2 second sample interval, 48
data samples taken at the 240 samples per second rate are averaged to
yield the recorded sample.


  The data is resolved to 14 bits.  The lower 2 bits of the
data word are reserved for marker bits, such as time marks.  I
equipped a WWVB wall clock with an optical pickoff to mark my recordings
at a once-per-minute rate.


  I developed a drum plot program for display and filtering of
recorded data.  This program can run simultaneously with the Dataq
recorder and display data from the file as it is being recorded.  It
can output filtered versions of the original file.  I find the
"Broadband" filter to be most useful, since it extends the
usual response of my 3.4 second seismometer out to periods of 20 seconds
or more.  It is available for downloading from the Dataq web
site.  It is also on the installation disc for the Dataq Lite
Software, in the catalog section.


Regards,


Bob McClure