use circuitikz picture inside tikzpicture

Question

In block scheme I like to add a node with call out shape, which contain details of electronic circuit. This electronic circuit is easy to draw with circutikz package. Here is my attempt to achieve this goal:

\documentclass[tikz,border=3mm]{standalone}
    \usetikzlibrary{positioning,%
                    shapes,shapes.callouts%
                    }
    \usepackage{fouriernc}
    \usepackage[scaled=0.83]{helvet}
    \usepackage[scaled=0.82]{luximono}
    \usepackage{marvosym,pifont}

    \usepackage[T1]{fontenc}
    \usepackage[utf8]{inputenc}
%---------------------------------------------------------------%
\usepackage[european,siunitx]{circuitikz}
\usepackage{siunitx}
\sisetup{detect-family,
     color = teal!40!black}
%---------------------------------------------------------------%
    \begin{document}
\begin{tikzpicture}
\coordinate (a) at (0,0);
\coordinate (b) at (4,0);
\draw (1,-0.1) -- (1,0.1);
\draw (2,-0.1) -- (2,0.1);
\draw (3,-0.1) -- (3,0.1);
    \draw[ultra thick,*-*] (a) -- (b);
\node[shape=rectangle callout,
      draw, rounded corners,
      callout pointer width=3.3 mm,
      callout pointer shorten=-2mm,
      font=\sffamily\footnotesize,
      align=center,
      callout absolute pointer={(b)},
      scale=0.5] at ([xshift=19mm,yshift=3mm] b)
    {termination circuit\\
    \begin{circuitikz}[sharp corners]
\draw[ultra thick, blue] plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, blue] plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw   (0,3)   node[right] {\SI{+5}{V}}
    to [R=$R_s$,o-] (0,+1)  node[right] {A}
    to [R=$R_k$,*-*] (0,-1) node[right] {B}
    to [R=$R_s$, -o] (0,-3)
                node[right] {\SI{0}{V}};
    \end{circuitikz}
    };
\node[shape=rectangle callout,
      draw, rounded corners,
      callout pointer width=3.3 mm, 
      callout pointer shorten=-2mm,
      font=\sffamily\footnotesize, 
      align=center,
      callout absolute pointer={(a)},
      scale=0.5] at ([xshift=-19mm,yshift=3mm] a)
    {termination circuit\\
    \begin{circuitikz}[sharp corners]
\draw[ultra thick, blue] plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, blue] plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw   (0,3)   node[right] {\SI{+5}{V}}
    to [R=$R_s$,o-] (0,+1)  node[right] {A}
    to [R=$R_k$,*-*] (0,-1) node[right] {B}
    to [R=$R_s$, -o] (0,-3)
                node[right] {\SI{0}{V}};
    \end{circuitikz}
    };
\end{tikzpicture}
    \end{document}

Questions:

• why both nodes are not the same (as I expected);

• why I receive error "unknown function 'south (in south east)' if I use for positioning of node possibilities offered by positioning library?

  \node[shape=rectangle callout, draw, rounded corners, callout pointer width=3.3 mm, callout pointer shorten=-2mm, font=\sffamily\footnotesize, align=center, callout absolute pointer={(a)}, scale=0.5, above left=-19mm and 3mm of a] {content of node};

Edit: I correct a bit my preamble where by mistake I had \usepackage{circuitikz} twice. The second one should be siunitx wit added setup. I like to have labels of resistors in sans sheriff font, but this hasn't happen. I do not knoe why not, but this is not a issue of this questionseparate question.

Answer 1

You are using circuitikz inside a node. The circuitikz environment is nothing but a tikzpicture environment in disguise. Using tikzpicture inside a node is not a good idea and it will cause odd things. You can use a box instead. I have created \mycircuita and \mycircuitb boxes (with 0 and 20V) and used them inside the callout node.

\documentclass[tikz,border=3mm]{standalone}
    \usetikzlibrary{positioning,%
                    shapes,shapes.callouts%
                    }
    \usepackage{fouriernc}
    \usepackage[scaled=0.83]{helvet}
    \usepackage[scaled=0.82]{luximono}
    \usepackage{marvosym,pifont}

    \usepackage[T1]{fontenc}
    \usepackage[utf8]{inputenc}
%---------------------------------------------------------------%
\usepackage[european,siunitx]{circuitikz}
\usepackage{circuitikz}
%---------------------------------------------------------------%
\newsavebox{\mycircuita}
\sbox{\mycircuita}{%
\begin{circuitikz}[sharp corners]
\draw[ultra thick, blue] plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, blue] plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw   (0,3)   node[right] {\SI{+5}{V}}
    to [R=$R_s$,o-] (0,+1)  node[right] {A}
    to [R=$R_k$,*-*] (0,-1) node[right] {B}
    to [R=$R_s$, -o] (0,-3)
                node[right] {\SI{0}{V}};
    \end{circuitikz}
    }
\newsavebox{\mycircuitb}
\sbox{\mycircuitb}{%
\begin{circuitikz}[sharp corners]
\draw[ultra thick, blue] plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.25*pi:-0.75*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, red]  plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{+1*sin(2*\x r)});
\draw[ultra thick, blue] plot[smooth,domain=-0.75*pi:-1.25*pi, samples=36] (0.25*pi+\x,{-1*sin(2*\x r)});
\draw   (0,3)   node[right] {\SI{+5}{V}}
    to [R=$R_s$,o-] (0,+1)  node[right] {A}
    to [R=$R_k$,*-*] (0,-1) node[right] {B}
    to [R=$R_s$, -o] (0,-3)
                node[right] {\SI{20}{V}};
    \end{circuitikz}
    }

\begin{document}
\begin{tikzpicture}
\coordinate (a) at (0,0);
\coordinate (b) at (4,0);
\draw (1,-0.1) -- (1,0.1);
\draw (2,-0.1) -- (2,0.1);
\draw (3,-0.1) -- (3,0.1);
    \draw[ultra thick,*-*] (a) -- (b);
\node[shape=rectangle callout,
      draw, rounded corners,
      callout pointer width=3.3 mm,
      callout pointer shorten=-2mm,
      font=\sffamily\footnotesize,
      align=center,
      callout absolute pointer={(b)},
      scale=0.5] at ([xshift=19mm,yshift=3mm] b)
    {termination circuit\\
\usebox{\mycircuita}
    };
\node[shape=rectangle callout,
      draw, rounded corners,
      callout pointer width=3.3 mm,
      callout pointer shorten=-2mm,
      font=\sffamily\footnotesize,
      align=center,
      callout absolute pointer={(a)},
      scale=0.5] at ([xshift=-19mm,yshift=3mm] a)
    {termination circuit\\
    \usebox{\mycircuitb}
    };
\end{tikzpicture}
    \end{document}

As an alternative, you could also use pic facility of tikz but using a box is simpler in this case.