Add an arrow label for impedence plane references

[Derek Kozel]

I’d like to request an added label that allows a reference plane and direction for circuit impedences. Here are two images I found online that show the general idea. There doesn’t seem to be a fixed standard so the actual styling can be adapted to best fit in with existing labels. Thanks!

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[cdelker]

Added a ZLabel element in 9dc4717. Example:

with schemdraw.Drawing() as d:
    d += (vin := elm.SourceSin())
    d += elm.RBox().right().label('50Ω')
    d += elm.Line().length(1)
    d += elm.Dot().label('A')
    d += elm.ZLabel(ofst=.4, length=.75).label('$Z_{A}$')
    d += (r1 := elm.RBox().down().label('10KΩ').dot().hold())
    d += elm.Line().right().length(2)
    d += elm.RBox().down().label('5KΩ')
    d += elm.Line().tox(vin.start)

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[Derek Kozel]

Thank you, this has been working well. I’ll be using the element about a hundred times in my thesis.