Enhanced AS-1 electronic circuit.
MuVentures Schools Seismometer
Magnetic-damping alternative for the AS-1 seismic sensor
Lehman Design (With suggestions for sensor- and damping-designs that apply equally well to vertical and horizontal instruments.)
Moving coil sensor based on speaker design.
Piezo-disk Seismic Sensor Design
Distance Sensor Calibration Mechanism
Graphite-Levitation Seismic Sensor
Suggested Links to Magnetometer Sites