The data for these tubes is obtained empirically. Each file, contains the block of data (average readings) and the diagram which shows the modeling results. An attitude towards every type of tube was subjective. Those tubes seeming more perspective were examined more carefully. Namely, greater number of points for characteristic curve was chosen, greater number of samples was examined, and the coefficients for modeling were selected more carefully. For other tube types, a limited number of data points were gathered, for familiarization. You can expand this model or pick up coefficients for the model, using the program TuParam.m (Tuparam.zip).