Transformerless input for seismic data acquisition system

摘要

In a long line data acquisition system, an input network is provided for coupling the lines to a data acquisition unit. The network includes the cascade combination of a first filter presenting a low pass frequency response to common mode voltage and a second filter presenting a low pass frequency response to difference mode voltage. The output of the second filter is coupled to an amplifier having high common mode rejection. The network substantially reduces, at the amplifier input, both common mode and difference mode noise picked up by the lines.