The BB-13 Seismometer is an enhancement of the S-13 short-Period Seismometer. A capacitance transducer that senses motion between the 5 Kg mass and the BB-13 frame, and an electronic feedback loop that drives the main coil/magnet transducer of the S-13 has been added. The result is an instrument that senses seismic acceleration over a bandwidth of dc to 20 Hz.
The BB-13 can be configured for vertical or horizontal operation.

This instrument was probably removed from service because of intermittent 'sticky' operation. Particles of rusted magnetic material were found in the gap between the force feedback coil and magnet. When the BB-13 was received, it was found to be setup for horizontal operation. After opening it to reconfigure the support rods for vertical operation the particles were found in the magnet gap. It was fortunate to find this before operating the seismometer as serious damage could have occurred to the windings of the feedback coil.

My local environment In Pacific Grove is quite noisy.
Since we are in the process of moving to Northern California, the BB-13 is currently located in the seismometer array operated by George Bush, KE6PXP at The Sea Ranch, CA.

When I first set it up here in Pacific Grove, it was located on the fireplace hearth. The only solid surface I could find.
With Larry's new A/D board and WinSDR I starting see events (between cars and trucks going by) from Baja, Fiji, Kurl, Reykjanes & Solomon Ils.
The BB-13 is a very sensitive broadband instrument.