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About FTA

Laplace-Young Errors and Logs

The FTA interfacial tension software can operate two ways:

  • Polynomials are fitted around the entire drop shape and these analytic expressions are used to obtain a solution to the Laplace-Young equation. This method does not yield the error between the actual drop profile and the ideal Laplace-Young profile because the variations in the actual drop profile are subsumed by the regression into the polynomial coefficients. Basically the variations (noise, errors) are averaged away. We refer to this as the Quick Mode because the calculation is very fast. It is suitable for Live analysis.

  • The classical Laplace-Young integration and optimization is carried out. This provides the error in the fit between the actual and ideal drop profiles. This is much slower, but does provide the additional parameters that are sometimes desired. The "residual" in the fit is the RMS (root-mean-squared) error, averaged over the pixels in the profile, between the actual and ideal profiles. It is reported in millimeters. A typical, good, value is 2 microns. Fits with errors over 10 microns are suspect.

The following logs are written to disk each time an IFT analysis is made. These files always use the same name, so previous data is written over. Also, the Laplace-Young optimization logs are not created when the Quick Mode is used. The logs allow you to inspect the profile and the fits in detail, line by line.

  • FtaSidePointsLog.txt: points found down the sides of the drop.

  • FtaApexPointsLog.txt: points found across the apex or vertex of the drop.

  • FtaLYPointsLog.txt: the Laplace-Young ideal profile.

  • FtaLYOptimizationLog.txt: Laplace-Young beta and radius of convergence iterations.

The logs and error calculations were added in Build 153.