Monday, January 30, 2012
Here are some pictures that illustrate the current state of my Inyo fbv seismometer. As you can see I have made a few (I hope, minor) alterations to the original. I have counterbored the screws in the base plate and have added three holes for possible future mounting arrangements when the instrument is put in a pressure sealed case. I also combined the two boom towers into a single piece because I do not like to mount thing with a single bolt.
I reversed the two bolts holding the spring tower so I don't have to look at the ends of the bolts sticking through from underneath. Less obviously I changed the screws on the clamps to 8-32 as #8 holes are easier to tap. Finally, I bolted the two steel parts together instead of welding them. This worked well as the magnet and coil assembly has a Gn of 16 N/A.
Monday, May 16, 2011
Here is a photo of my roughly half size rip off of a Sprengnether seismometer. Unlike the original, this instrument uses an lvdt as the sensor. That's a six inch scale in the foreground.
Also, here is a link to the paper that I presented in 2005 about using crossed flexures as pivots for a seismometer.
Friday, November 9, 2007
Here are a few pictures of the pair of Lehman seismometers that I am currently operating in Vermont. The construction is primarily of square aluminum tube that you can get in most big box hardware stores.
The two instruments differ in the construction of their motors and in the sensors used. The East-West device has an LVDT sensor while the North-South machine uses a photo-optical sensor. Both machines have the same sensitivity.
That is a six inch scale on the workbench in front of the seismometer.
Here is a picture of the upper pivot. It is made of crossed pieces of .001" thick steel shim stock. You can see the wires from the damping motor coil where they cross over the pivot.
The last picture in this group shows the two instruments in their insulated box. There are heaters on the top of the box. The temperature in the box is regulated to 80°F at a point just over the instruments. The sheet aluminum on top of the units is there to reflect thermal radiation from the heaters.