Calculation of a Spectrum from Experimental Data

We first address the problem of converting a set of experimental data in the form G , G o into a discrete relaxation spectrum, i.e., into a set of parameters Gj, T . This requires the deconvolution of the summations in Eq. 4.41. 

It is very important to note that the success of this transformation is limited by the following inevitable features of oscillatory shear data. 

Data are obtained only at a certain number of discrete frequencies. 

Data are available only between maximum and minimum frequencies that are imposed by the capabilities of the instruments used. This range of frequencies is called the experimental window . 

There is always some imprecision (called scatter or noise) in the data. 

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