**2. Magnetic induction spectroscopy**

108 Advanced Aspects of Spectroscopy

and resistivity and inversely with its area

electrodes Bio-impedance analysis.

Ω/cm2)[4]

In a homogeneous conductive material the impedance (Z) is proportional to its length and

**Figure 2.** The impedance (Z) of homogeneous conductive material is directly proportional to its length

Z=ρL/A=ρL2/V (1)

According with the Figure 2 Z=impedance, L=length, A=area, V=volume ρ=resistivity=1/σ (conductivity). An empirical relationship can be established between the ratio (L2 / V) and the impedance of the saline solution which contains electrolytes that conduct electricity

Hoffer et al. [2] and Nyboer [3] were the first to introduce the technique of four surface

A disadvantage presented by this technique is the use of a high current (800 mA) and a high voltage to decrease the volatility of injected current associated with skin impedance (10 000

Harris et al.[5], (1987) uses a four terminals device to measure impedance for the purpose of

Asami et al.[6] , (1999) used a pair of coils submerged for monitoring the current induced in the coil pair, which he called electrode-less method, however still requires physical

To measure the complex spectrum of the permittivity of a biological culture solution Ong et al.[7], uses a remote sensor resonant circuit, to obtain the impedance of the environment by

through the sample. Therefore impedance (Z) = L / A = L2 / V.

eliminating the effect of electrodes in an aqueous medium.

connections between the coils and electronic instruments.

observing the resonant frequency and the frequency of zero reactance.

inversely proportional to its cross sectional area (A) (Fig. 2).

"The Magnetic Induction Spectroscopy (MIS) aim is the non-contact measurement of passive electrical properties (PEP) σ, ε and μ of biological tissues via magnetic fields at various frequencies.[9]"

The basic requirements of this method are:


**Figure 3.** Measurement System: composed of a coil arrangement, network analyzer, and a pc

#### **3. Measurement system**

Following the protocol of the method used in Figure 3 we present our system Equipment-Interface into three sections:

a. Computer: Using the platform that provides National Instrument [10] - LabView V8.6, displays and processes the information obtained from the coil system from the Instrument.

**Figure 4.** Virtual Instruments LabVIEW (National Instrument VI), a) Front panel (user), b) Block diagram panel (interconnections), uses them to automate the acquisition and management of information.

b. Instrument: Commercial Equipment, RS ZV Vector Network Analyzer [11] "Rohde & Schwartz" which performs the frequency sweep from 100 kHz to 4 MHz range, applying it to the exciting coil, the same equipment then captures the data or information from the receiver coil and sends to the computer via General-Purpose Interface Bus Universal Serial Bus or GPIB-USB.

110 Advanced Aspects of Spectroscopy

information.

**Figure 4.** Virtual Instruments LabVIEW (National Instrument VI), a) Front panel (user), b) Block diagram panel (interconnections), uses them to automate the acquisition and management of

**Figure 5.** Network Analyzer "Rohde & Schwartz", as a frequency sweep source

c. Coil System: Fig. 6 show this system, consisting of three coils, an exciter, a receiver completely perpendicular to the exciting, adjusting it to the mutual inductance between two coils is minimal, and a third coil to function as "mirror-sensor" of the magnetic field generated by the exciting coil.

**Figure 6.** Representative schematic of the three coil arrangement
