For a project we needed to read out our PC-222 multimeter. It supports RS-232, but the protocol is not documented at all and the software is proprietary. After a little research on the web, we found some information in a comment on Amazon. With this and a little trial–and–error we found out how it works.
Last week, I posted an article about sigmoid functions and how to use them. Nevertheless, it is hard to guess the parameters for a given problem. So, people use software such as Origin  or QtiPlot to fit.
Personally, I use Origin/QtiPlot only for plotting and Excel/OO–Calc for evaluation/calculation, because both programs are much more comfortable and powerful. However, both lack the possibility to fit sigmoid functions, automatically.
It is possible to do such fits for nearly any function using the solver, though, but only a few people I’ve met knew how to do this or that it is even possible. But, I think the solver is a very handy feature and, therefore, I want to give here a short introduction into using it for fitting a sigmoid function to a set of data.
- " OriginLab - Origin and OriginPro - Data Analysis and Graphing Software " http://www.originlab.com/