Shackleford-Gundersen Seismometer Electronics Board

Last Updated: 04/26/06

Please note that this board is no longer in production

Block Diagram

Online Documentation


This board implements the complete electronics needed to build a Shackleford-Gundersen (SG) seismometer:

The board has two RCA jack inputs (the lower right hand jacks in the photo above) that are connected to the receiving antenna plates mounted inside the sensor. The first amplifier stage, the summing amp, is designed around a low noise high performance op-amp.

Outputs to Sensor:
The board supplies two signals that go to the sensors. It supplies a low impedance output signal used to drive the damping coil, and, a regulated +5 volt signal used to power the TTL oscillator mounted on the pendulum. The connector used for the damping coil and the oscillator power is a 4 pin .156 Molex connector. This connector is located near the upper right hand corner in the photo above.

Output Signals:
The board has two output signals that go to an Analog to Digital Converter Board or chart recorder. The Low Frequency Port integrates the data from the sensors making it more sensitive to the long period waves produced by teleseismic (distant) earthquakes. The High Frequency Port bypasses the integrator and is used for local or regional events. The output signal RCA jacks can be seen in the bottom center of the board in the photo above. Both outputs are designed to drive +- 10 volts maximum into a 600 ohm load, and, are able to drive over 100 feet of coax cable.

Tilt LED:
The board has a two color LED (Light Emitting Diode) that will turn either red or green indication that the sensor is tilting too much.

Power Requirements:
The board requires a 24 to 28 volt center tapped transformer with 300ma, or more, of output current. I have a wall mounted transformer that I sell that can power up to two boards.

Board Dimensions:
5 3/4 x 7 3/4 inches or 14.5 x 19.7 cm.

Schematic of the SG Electronics Board:


The SG Electronics board can be ordered with either the Low Frequency or High Frequency port or with both ports. The board with one port (either High or Low) costs $125.00. A complete board with both output ports costs $145.00. I'm selling the board built and tested without a box to keep the cost down. A wall mounted power supply that will work with this board costs $15.00. Please add $8.00 for shipping and insurance.

I also have the following parts available to help you build your SG sensor:

Additional Information:

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Larry Cochrane -