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electrodes M N or P1 P2). As far as “traditional” instruments are concerned, the applied
current and thus the corresponding voltage have always been continuous, with reversed
polarity for each measurement. POLARES32 uses a sinusoidal alternating current with
adjustable frequency.
Why is POLARES32 an innovative instrument?
The use of alternating current has shown particular advantages in terms of speed of
execution of measurements with the same quality of results. Compared to conventional
DC systems, this increased speed can reduce the time to perform the same set of
measurements in the field by at least a factor of 10 (or even 20, in most cases).
Furthermore, the measurement of the relationship between the detected voltage and the
injected current, in a sinusoidal state, both in terms of amplitude and phase (delay of one
signal on the other), allows the simultaneous detection of resistivity and induced
polarisation of the ground.
What are the main strengths of POLARES 32?
- COMPLEX RESISTIVITY ACQUISITION: being designed as an AC system,
POLARES32 involves both the conduction and polarisation properties of the material
under investigation. Since the complex resistivity modulus deals with the electrolytic
properties of the pore-filling fluids, the phase shift between the voltage and current signals
is directly influenced by the polarisation of the material. Thus, each individual data set
can be used to analyse both resistivity and induced polarisation.
Resistivity (as the reciprocal of conductivity) is a complex, frequency-dependent property
of a material and is described by the following equation:
where σ * and ρ * define complex conductivity and resistivity respectively, | σ | is the
modulus of conductivity, φ is the phase shift between voltage signal and current, σ’ and
σ” are the real and imaginary part of the complex r
esistivity.
