plot artefact if plotting high frequency signal after simulation

[Holger Vogt]

A simple circuit:
Votage source with sinewave 1V amplitude, 1 kHz frequency, into load resistor 1 Ohm, labbelled with 'out'.
Transient simulation for 1 s, time step 100 us.

The plot of V(out) versus time yields a (sine) wave with 1 V amplitude and about 56 periods, that is a frequency of about 18 Hz (see plot output attached).

The plotting procedure suggests a wrong oscillation frequency.

[Holger Vogt (h+vogt)]

The bug exists in all current KiCad versions, MS Windows

[Holger Vogt (h+vogt)]

The eeschema files

[Holger Vogt (h+vogt)]

Well, 56 periods are 56 Hz ...

[Wayne Stambaugh (stambaughw)]

I believe this has something to do with the graphing code. When I zoom in, the waveform frequency is definitely 1KHz. In the view you provided, you should not even be able to see a waveform. I should look like a solid plot because the is 1000 sine waves in the small plot area. It looks like the graph plotting code is trying to compensate for waveform density. Anyone else have any ideas about this?

[Jeff Young (jeyjey)]

By shrinking the window you can get some plots that are -really- wrong.

[Jeff Young (jeyjey)]

The mathplot module skips intermediate Y points until the X point changes. Sadly, in the "overloaded" case this may be several waves later, resulting in bogus graphs.

[KiCad Janitor (kicad-janitor)]

Fixed in revision 2ac270ce8ea1fe81fd7b6946899532af56f8de8e
https://git.launchpad.net/kicad/patch/?id=2ac270ce8ea1fe81fd7b6946899532af56f8de8e