The Earth Lab 5s (ETL3D/5s) seismic sensor. Design and test

This work presents a new low cost and low power consumption wide-band (5s) three-component seismic sensor, named ETL3D/5s. The sensor is suitable for seismic regional monitoring (local and regional earthquakes), HVSR measurements, seismic microzonation studies and Structural Health Monitoring (SHM) of civil structures. ETL3D/5s includes a set of three 4.5 Hz geophones and an electronic circuit that in-creases the geophone’s natural period . The sensor exhibits a period of 5 s and a power consumption as low as 75 mW. Changes in ambient temperature have little effect on the frequency response because a temperature compensation system is also implemented. A small and sturdy cylindrical housing contains the electronic boards and geophones. The housing design was supported by a modal FEM analysis, in order not to affect the frequency response. The chosen materials and parts guarantee protection against atmospheric agents and watertightness (IP67 degree). The sensor noise model, partially confirmed by a field test, predicts a power spectral density of 10 (nm/s)/√Hz at 1Hz.