3.3.12 Preliminary Data Analysis

A preliminary analysis of the time constant (-s) (emission rate (-s)) of the transient can be done in two ways using: (1) simple one-exponential fitting, or (2) the Fast_DC routine. In the first case it is assumed that the data contain only one discrete exponential component and the best fit is found on this basis. In the later case the software analyses the transient and can decide by using statistical criteria the number of exponential components in the transient. The way the data is to be analysed is defined by the first two buttons on the left-hand side of the top toolbar in the Analysis folder or by the appropriate item in the Analysis menu.

 

The fitting procedure is invoked by indicating the part of the transient which has to be analysed. This is done in a similar way as the Zooming and Unzooming action but in this case the right mouse button is used by dragging over the region to be analysed. The section of the transient chosen for the fitting procedure is represented graphically on the Horizontal bar (see Mouse events for more details).

 

The numerical results of the fitting are given in the corresponding frames on the top part of the Analysis folder. Option buttons in the Fast_DC frame forces the numerical routine to find in the given transient one, two, or three components, the last case (Auto), the software decides how many components there in the transient could be.

The results are also presented graphically on the Main Graph as the fit to the transient, and also as a bar-type diagram. The position of the bar on the Sample axis represents the time constant of the given transient component. If the display uses the sample number as the horizontal axis it will be necessary to interpret this in seconds by multiplying by the time for one sample used for that measurement by the sample number. The time for one sample will be displayed in the Acquisition folder. The bar height represents the component amplitude and can be read directly from the right-hand vertical axis of the Main Graph. The Residuals button of the Analysis toolbar can be used to examine the quality of the fit. The line represents the absolute values of deviations of the fit from the transient. In the case of the Fast DC routine it is also possible to view the emission rate diagram from a button in this toolbar, and save it (the next button) as a spectrum file for further comparison with the inverse Laplace spectra. See File name extension scheme - data and spectra for more information. NOTE: to store this spectrum file the data file must be saved previously.