Spectrum Software
Industrial Strength Simulation




Spectrum Software has released Micro-Cap 11, the eleventh generation of our SPICE circuit simulator.

For users of previous Micro-Cap versions, check out the new features available in the latest version. For those of you who are new to Micro-Cap, take our features tour to see what Micro-Cap has to offer.




Questions and Answers - Fall 2011


Question: I am running a transient simulation for 10ms. The Maximum Time Step has been set to 1us so I expect to get a minimum of ten thousand data points in the plot. While the simulation is running, the expected number of data points seems to be present, but once the simulation is finished, Micro-Cap reduces the number of available data points. Why are the data points being reduced?

Answer: There are two possible reasons for the data point reduction.

1) The Reduce Data Points settings have been modified:
Under the Transient menu, there is a Reduce Data Points command. This command controls the number of data points that are retained at the end of the simulation. The default setting is to keep all data points that have been calculated. In order to keep all available data points, both the Save and Display fields should be set to 1st.

2) A waveform using a Fourier function is being plotted:
If one of the waveforms specified in the Transient Analysis Limits dialog box uses a Fourier function (HARM, FFT, THD, IHD, etc), all of the waveforms will be resampled at the end of the simulation so that the Fourier functions can be processed.

For the Fourier calculations, the number of data points that the waveforms will be resampled to is set in the FFT page of the Analysis Properties dialog box. The Number of Points field in this page controls the number of sampled data points, and the value set in this field must be a power of 2. If no Fourier waveforms are being plotted, the settings in this page are ignored.

The FFT Window can be used to create a Fourier waveform which will not resample all of the waveforms specified in the analysis limits. The FFT Window can plot the basic Fourier functions such as the harmonics, the real and imaginary portions of the FFT, the total harmonic distortion, the individual harmonic distortion, and the FFT phase. An FFT Window can be created through the Transient / FFT Windows / Add FFT Window command or by right clicking on the expression string in the plot window and selecting Add FFT Window in the popup menu.

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