Skip to content

SPICE Plot: Right Y-axis label is garbled and power signals display incorrect units (V instead of W)

Current behavior: When plotting multiple signal types (e.g., current and power) that share the right-side Y-axis in the SPICE simulator, the axis title becomes cluttered and unreadable as the text for each unit overlaps.

image

Additionally, a user-defined signal representing power (e.g., V(/Out) * I(R2)) is incorrectly labeled with Volts (V) as its unit in the cursor's measurement tooltip, instead of Watts (W).

The attached screenshot illustrates both issues: the garbled "Corrente/mA/Energia(W)" axis title and the cursor measuring the red power signal with a value in "V".

Expected behavior: The right-side Y-axis labels for different physical quantities should be displayed clearly without overlapping. Also, signals representing power should be correctly identified and displayed with the unit Watts (W) in all contexts, including cursor measurements.

Steps to reproduce

  1. Open the SPICE simulator in any project (like the one of the image below).

image

  1. Run a transient simulation.
  2. Plot a voltage signal (e.g., V(/Out)), which will occupy the left Y-axis.
  3. Plot a current signal (e.g., I(R2)), which will create and use the right Y-axis.
  4. Add a user-defined signal for power by entering an expression like V(/Out) * I(R2).
  5. Observe the right Y-axis title, which now becomes cluttered as it tries to display units for both current (mA) and power (W).
  6. Add a cursor to the plot and place it on the power signal curve.
  7. Observe the measurement tooltip, which confirms the value with a "V" unit instead of "W".

KiCad Version

Application: KiCad PCB Editor x86_64

Version: 9.0.4, release build

Libraries:

wxWidgets 3.2.8
FreeType 2.13.3
HarfBuzz 11.4.5
FontConfig 2.17.1

Platform: Arch Linux, 64 bit, Little endian, wxGTK, Wayland, KDE, wayland OpenGL: AMD, AMD Radeon Graphics (radeonsi, renoir, ACO, DRM 3.64, 6.16.4-arch1-1), 4.6 (Compatibility Profile) Mesa 25.2.1-arch1.5

wxWidgets: 3.2.8 (wchar_t,wx containers) GTK+ 3.24
Boost: 1.88.0
OCC: 7.9.1
Curl: 8.15.0
ngspice: 45
Compiler: GCC 15.2.1 with C++ ABI 1020

Build settings:

KICAD_USE_EGL=ON
KICAD_IPC_API=ON

Locale:

Lang: pt_BR
Enc: UTF-8
Num: 1.234,5
Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)