In vitro measuring cells

Some material constants with a homogeneous cylinder of biomaterial is a = GL/A, e = CL/A, and the resistivity p = RA/L. The ratio A/L [m], or L/A [1/m] is the cell constant of a measuring cell. In general, the cell constant can be determined for other geometries than the cylinder, so that it is easy to derive the unknown conductivity, permittivity, or resistivity from measured results. In the latter case, it is of course important that the measuring cell is completely filled with the sample biomaterial. 

If the measurement is to be performed under ex vivo conditions, the tissue is to be kept alive by controlling the temperature and the extracellular fluids. Also with dead samples, temperature and extracellular liquid control may be necessary. For dry dead samples, control of the ambient air humidity may also be necessary. 

One way of reducing the effect of electrode polarization is to increase the impedance of the sample by increasing its length. To compensate for the polarization impedance further, several methods are possible  

Measure electrode polarization impedance separately and subtract 

Substitute the unknown with a known sample for calibration 

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