View Seismometer Data
from
Palo Alto CA
Below 2 images are horizonal Lehman Seismometers with 25 second resonant periods with Chapman magnet and sensor design using NdFeB magnet material. See here for design details.
East-West Lehman Seismometer
North-South Lehman Seismometer
Below are image files for a Force-Balance vertical seismometer built along the design of Dave Nelson and Brett Nordgren. The seismometer has both a low and high sensitivity over a frequency range of 100 seconds to 20 Hz. The low-gain sensitivity is 7.50 volts/cm/sec. The high-gain sensitivity is 375 volts/cm/sec. Signal clipping is 1.3 cm/sec for low-gain and 267 um/sec for the high-gain side.
Low-gain Channel
14.4um/sec per line
High-gain Channel
1.15 um/sec per line
Infra-Sonic Atmospheric Pressure vs. Time
The above display is a plot of differential atmospheric air pressure recorded by comparing at moment of measuring and that of a 470 ml reference volume with a calibrated leak. The time-constant of the reference volume and calibrated leak is 220 seconds. See here for sensor construction details.
The seismometer data is updated every 10 minutes. A sharp short spike is probably us checking the seismometer vault (wine cellar). Send an e-mail if you have any questions.
