Probing and waveform viewer

When moving a wire or a component its voltage/current get probed with the same click and drag action. It’s quite annoying as it messes up the waveforms that you have carefully set up in the waveform viewer. However, seems like this doesn’t happen all the time, especially with wires. I would suggest to use some keyboard key to enable probing (as you already need to use Alt to probe voltage between two nets).

Also, waveform viewer often assigns same color to several waveforms in the same window.

You can disable editing(so that mouse syntax is exclusively for probing) by holding down the alt key.

Otherwise, I’m trying the keep the syntax sufficiently distinct so that no such mode is required. You and edit or probe without having some extra state latched.

That’s too bad. I think it’s just too worksome and slow to always setup the waveforms again after editing the circuit. Maybe there could be an option to adjust the probing behavior in the future?

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I thought you were asking for something else.

Of course you can save the plot settings. Press the little floppy disk icon. After you rerun the simulation, press the space bar to get back to the same settings but with the new data.

You can can different plot setting files under different names. I think you can drag the .pfg file into the waveform viewer and it will adopt the settings of that file.

Saving and loading plot settings just to circumvent the problem is too slow and complicated IMO. Even though you have to use function keys to modify the circuit in LTspice, it’s still much faster to work with because you don’t mess up the waveform viewer every time you move wires or components.

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I agree with Olli. One thing that can be done is to keep the zoom when the simulation is performed again. In the current version, if you zoom in and simulate again (even without changing the circuit), the waveforms are maintained, but the zoom is not.

(edited due to a typo)

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Hello everyone,

I was wondering if there is some kind of differential voltage probe implemented in QSPICE. If yes, how can I activate it?

Thank you in advance for answering!

While pressing the ALT key, press left mouse button at node #1, drag to node #2 while holding ALT and left mouse button, then release.


Hello Jope,

Thank you very much for your answer! I tried to apply your advice, unfortunately without success. Every time I move the cursor with the left mouse button pressed, regardless of whether I hold down the ALT key or not, the previously selected element / wire piece is moved.

Hello Jope,

I take back my statement. Your suggestion works, but only when the waveform viewer window is open, which makes sense. I had accidentally closed the window in the meantime, that’s why it didn’t work.

Hi Mike,

Please, could you consider adding an option to either:

  • Probing enabled only with some keyboard key pressed, or
  • Probing disabled with some keyboard key pressed.

I would prefer the former but the latter would work as well. This way it would be possible to move components in the schematic without making unwanted changes to the waveform viewer signals. It would speed up working with QSPICE and significantly decrease the amount of frustration. Please :slight_smile:

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My favourite solution would be two modes, one for editing, on for probing, implemented as two tabs in the main schematic window.
After a simulation run, a copy of the simulated schematic is made (e.g. as *.qschsim) and used as basis for the probing mode. The probing mode is then activated automatically. Now I can probe without extra buttons to press, without the fear of accidentally moving something. It would have its own probing specific context menu etc. This would increase usability while also reduce the risk to mess up net names and loosing sync with the simulation data.
For editing I would go back to edit mode, editing the original schematic file, leaving the schematic of the probing mode untouched. So, until I simulate again, I have a pair of read-only schematic and data. This would also be great for archiving slow running simulations. With the edit mode moving a wire doesn’t plot that node, the DC OP does not pop up etc.