Within uSimmics 5.8 a [Remove] button is added to ‘Parameter Tuning’. When no components are present in this ‘Parameter Tuning’-window and the [Remove] button is used, uSimmics crashes/terminates.
Parameter tune does not appear to support negative values.
Negative values are useful as error terms when trying to fit a circuit model to the performance of a physical circuit. i.e.: a negative capacitor in parallel with a capacitor. uSimmics does appear to simulate negative value capacitors correctly.