Poster: NanoTEM
A Very Fast Turn-Off TEM System

One traditional limitation of transient electromagnetic sounding methods is the long turn-off times of the transmitted signals. For shallow soundings, and highly resistive areas, this has prevented effective use of the method. This limitation has been overcome in the newest series of Zonge transmitters, the NT-20. These transmitters complete the current flow turn-off into a 20 meter loop in about 1.5 microseconds. This rapid turn-off, and the high speed analog-to-digital conversion in the GDP-32 receiver, allows data collection at depths less than 2 meters and in areas with electrical resistivities in excess of 20,000 ohm-meters.