Hello.
I have been interested in vacuum tube electronics since my youth. Since before the year 2000, I have been looking for simulation software for electronic circuits. I met and managed to use a wide range of such software. But they all suffered from the same disease - a very limited model library for electronic tubes. That's why I had to design myself the necessary models for the electronic tubes I used. Almost all the mathematical equipment I needed as a professional engineer (currently retired) I found in SMath, with the exception of the possibility to solve the systems of numerous nonlinear equations with numerous unknowns, necessary to prepare the models for the simulation of those electronic tubes. In the attachment, I have illustrated an attempt to solve with the help of SMath the problem of simulating a double triode of the ECC81 type. In essence, I searched (and found) enough technical references on the Internet from which I could extract information about the anode characteristics of electronic tubes. I transformed all the characteristic curves into specific numerical data vectors / matrices. Starting from here, I used non-linear regressions specific to the functioning of these tubes. I equated these mathematical expressions (quite complicated) point by point, with the numerical data obtained from the technical data sheets of those tubes, thus obtaining systems of numerous equations with numerous variables, which (by solving) provided me with the mathematical model of the functioning of those tubes. It can be seen in the example attached here that SMath was not able to solve such a system. In the same attachment, I have inserted an image of the same system of equations solved with the help of the MathCad program. It can be seen by studying the graphic representation in this image, how close the mathematical model is to the interpolation of numerical data. In the image, the numerical vectors (interpolated) were represented with dotted lines of the same color, while the solutions obtained by applying the regression were shown with continuous lines. Maybe I didn't know how to apply SMath skills to solve this system. That's why I'm waiting for someone else to provide me with an example solution using this program.
Greetings.
Mathcad Block sample.sm (133 KiB) downloaded 93 time(s).