Hello PSN, Here is something close to the core interests of this group, reviewing someone else's seismometer design. Last January, I decided it was finally time to build a VBB velocity instrument. Because Sean-Thomas was kind enough to share with the PSN the design of the STM-8 Leaf Spring Seismometer, particularly his Mathcad worksheets for the closed loop response, I could not resist the idea any longer. To help understand the ins and outs of a VBB design, I used an old force-balance accelerometer I previously made a year or two ago as a test bed. Its displacement transducer and feedback coil were already in place, and intact. I was going to replace my instrument's displacement transducer with a VRDT per Sean-Thomas' design, because of the excellent resolution it has over mine. Yet, over time my original design worked well enough to detect teleseismic events, see links on my Web page for some sample seismograms it has made. I am the first one to say that this design is no rival to the STM-8. I wrote the paper to show others that building a VBB seismometer based on Sean-Thomas' design, is very achievable. I must thank Chris Chapman for reviewing the paper. He helped me to improve the performance of the displacement transducer, as well as finding other errors in the text and circuit design. Below is the Web page address. http://hometown.aol.com/acole65464/OS_2000.html I would like to hear your comments and opinions. Regards, Allan __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>