\begin{circuitikz}[scale = 0.35, transform shape]
%  \draw[help lines] (0,0) grid (8,6);
%  \foreach \x in {0,...,10} \draw (\x,-1) node {\x};
%  \foreach \x in {0,...,7} \draw (-1,\x) node {\x};

  % uref
  
  \draw(0,3) to[V_<=\large{$U_{ref}$}] (0,5);

  % Switch
  \draw (3,4) node[spdt,xscale=-1, yscale=1, anchor=in] (z0) {};
  \draw (z0.in) node[anchor=south] {z0};
  \draw (z0.in) to[R=R] (5,4) to[C=C](5,2) to (5,2) node[rground]{};
  \draw (5,4) to[short] (6,4);
  %-- (6,4);
   
  %alle schalterausgaenge nr. 1 verbinden
  \draw (z0.out 1) |- (0,5);
  % mit u_ref verbinden
  %\draw (z0.out 1) -| (0,5);

  
  %alle schalterausgaenge nr. 2 verbinden
  \draw (z0.out 2)  to [short] (1.8,2) node[rground]{};
%  \draw (z0.out 2) |- (0,3);

  %
  mit 0V verbinden
  %\draw (z0.out 2) -| (0,3);

  % ground-ref an spannunsquelle
  \draw (0,2) node[rground]{} to [short] (0,3);

  % ausgang
  \draw(6,4) to[short,-o] (7,4){};
  \draw(7.5,3.5) node[]{\Large{$U_a$}};
  \draw[-{Triangle[scale=2.5, length=2, width=2]}](7,3.8) -- (7,3.2);
  \draw(7,3.8) to[short,->] (7,3.2);
  \draw (7,3) to[short,o-] (7,2) node[rground]{};
  
\end{circuitikz}
