Weakly electric fish use a process called 'active electrolocation' to orientate in their environment and to localize objects
based on their electrical properties. To do so, the fish discharge an electric organ which emits brief electrical current
pulses (electric organ discharge, EOD) and in return sense the generated electric field which builds up surrounding the
animal. Caused by the electrical properties of nearby objects, fish measure characteristic signal modulations with an
array of electroreceptors in their skin. The fish are able to gain important information about the geometrical properties of
an object as well as its complex impedance and its distance. Thus, active electrolocation is an interesting feature to be
used in biomimetic approaches.
We used this sensory principle to identify different insertions in the walls of Plexiglas tubes. The insertions tested were
composed of aluminum, brass and graphite in sizes between 3 and 20 mm. A carrier signal was emitted and perceived
with the poles of a commercial catheter for medical diagnostics. Measurements were performed with the poles separated
by 6.3 to 55.3 mm. Depending on the length of the insertion in relation to the sender-receiver distance, we observed up to
three peaks in the measured electric images. The first peak was affected by the material of the insertion, while the
distance between the second and third peak strongly correlated with the length of the insertion.
In a second experiment we tested whether various materials could be detected by using signals of different frequency
compositions. Based on their electric images we were able to discriminate between objects having different resistive
properties, but not between objects of complex impedances.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.