The UPEX® 745 DF is a deep active search system, based on the electromagnetic pulse induction principle designed and produced by us in Germany. The system is used to detect ferromagnetic and non-ferrous metal objects, primarily in unexploded ordnance clearance and subsurface geophysical surveys. With the UPEX® 745 DF, Ebinger completes its traditional range of pulse induction-biased measuring systems as far as resolution and detection depth are concerned. “German innovation from the Ebinger ideas laboratory”.
The circular coil arrangement substantially betters the signal-noise ratio (S/N) up to 50 % and thus allowing a significant increase in detection depth. The 5 time gates and a decoupling of the receiver coils substantially ameliorate detection and resolution. The dimensioning and the geometric arrangement of the inner receiver coils in conjunction with an early measurement also contribute to the enhanced performance and boost the resolution of small, near surface objects. The size and arrangement of the external receiver coils are adapted to the detection of larger and deeper buried targets. The geometric dimensioning of the system implies a significant increase in productivity due to the large scan area covered.
One of the basic requirements when using electromagnetic methods to detect metallic anomaly masses is a high contrast in the electric parameters of the objects to be detected compared to the natural subsurface conductivity. Iron has an extremely high conductivity of 107 S/m respectively an electrical resistance of 10-7 Ωm. This corresponds to a difference of 7 orders in magnitude compared to the best conducting soils / rocks. The same applies to its magnetic permeability (magnetite μr =5, iron μr =120). This extremely high contrast with regard to electric conductivity and magnetic permeability relative to naturally occurring soils/rocks forms the basic requirement for detection when using electromagnetic methods.
This method of measurement belongs to the family of transient electromagnetic methods (TEM), which operate within the time range. A source field is used, which induces current systems into the subsoil, whose propagation depends on the conductivity distribution in the subsoil. In the case of inductive transmitter coupling a constant direct current flows in a horizontal transmitter coil.
The constant transmitter current is switched off or over as abruptly as possible and causes the constant primary magnetic field to collapse, which has almost the geometry of a vertical magnetic dipole (VMD). At the same the time-independent primary magnetic field generates a current system according to Ampere‘s law and Faraday‘s induction law. Depending on the subsoil, it propagates both vertically and laterally (diffusion) as time progresses inducing eddy currents into the conductive subsoil in accordance with Maxwell‘s equations.
This current system decays due to ohmic losses, which in turn produces a secondary magnetic field, which also decays with time. The time depending changes in the magnetic field components induces a decay voltage (transient), which will be measured in the receiver coils (here the change in the vertical magnetic component over time).