Working Group Seismics

and Geophysics

at the St.-Michael-Gymnasium Monschau

The amplifier-filter-unit of the seismograph is simply constructed from few component parts. The voltage supply for the Ic's can be bought as a kit for self-assembly at an electronic shop. - The amplification-factor kv is adjusted by the ratio (R2 + R3) / R2 , the cutoff frequency fcutoff of the low-pass filter is determined by
1 / [2π · (R4 · C3 · R5 · C4)0,5]
The rest can be taken from the following circuit diagram.


Fig. 45: Circuit-diagram of the Amplifier-filter-unit of the seismograph