5
Mode of operation
17
5
Mode of operation
In this section the physical principle of detecting subterranean voids with
FS-Reflexion
will be
described. The best measurement results you will receive, if you know how the measured values
are recorded and how they has to be analysed.
Figure 7: Schematic representation of the mode of operation
In Figure
you can see the schematic representation of the mode of operation. The
transmitter
generates vibrations in different frequencies, which will be transfused into the ground. During
this process each frequency will be generated only for a certain period of time until the next
frequency will be generated. While using the operating mode
Fast Scan Mode
the unit will not
pass through all available frequencies.
Depending on the condition of the subsoil, the different seismic waves will be transmitted
more or less into the ground. Especially applicable are dry and compact soils. Loosy or wet
soil types, like e.g. swampland or sand are less suitable. In case of a serious change inside
the ground, like e.g. caves, inclusions or fillings, the vibrations will be well transmitted or
absorbed. In case of an existing void, it will start to resonate in its own frequency. As a result
an heterodyne vibrancy will be delivered to its environment. This vibrancy can be measured
by the
vibration transducer
as soon as it reaches the surface of the ground. This amplification of
the origin vibration will be represented in the
frequency-energy-graph
of the
control unit
as a high
amplitude.
How deep the seismic vibrations can be transmitted into the ground, does strongly depend
on the condition of the soil (resistance, humidity). The more compact the soil is, the deeper
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