MWE
\documentclass[border=2mm]{standalone}
\usepackage{tikz}
\usepackage{tikz-timing}
\usetikztiminglibrary{nicetabs}
\newcommand\gtikzset[1]{%
\begingroup%
\globaldefs=1\relax%
\pgfqkeys{/tikz}{#1}%
\endgroup}
\begin{document}
\begin{tikztimingtable}[
scale=2,
timing/rowdist=3ex,
]
\textnormal{} & @{\gtikzset{timing/rowdist=1}}\\
\textnormal{RS--232 Signal} & @{\gtikzset{timing/rowdist=1}}\\
\textnormal{} & @{\gtikzset{timing/rowdist=1}}\\
\textnormal{} & [y=4\yunit][line width=1pt] U L 2H 2L 5{2H} 2L 2L 2H 2{2L} L U \\
\extracode
\begin{pgfonlayer}{background}
%Left
\node[anchor=east] at (row1.north west){\scriptsize +15V};
\node[anchor=east] at (row3.west){\scriptsize --3V};
\node[anchor=east] at (row3.north west){\scriptsize 0V};
\node[anchor=east] at (row2.west){\scriptsize +3V};
\node[anchor=east] at (row4.south west){\scriptsize --15V};
%Right
\node[anchor=west] at (28,1){\scriptsize +15V};
\node[anchor=west] at (28,-0.5){\scriptsize +3V};
\node[anchor=west] at (28,-1){\scriptsize \phantom{+}0V};
\node[anchor=west] at (28,-1.5){\scriptsize --3V};
\node[anchor=west] at (28,-3){\scriptsize --15V};
%Horivontal
\shade[right color=red!60,left color=red!60](28,-0.5) rectangle(0,-1.5);
\shade[right color=green!60,left color=green!60](28,1) rectangle(0,-0.5);
\shade[right color=green!60,left color=green!60](28,-1.5) rectangle(0,-3);
%Vertical
\shade[right color=yellow!60,left color=yellow!60](2,-3) rectangle(1,1);
\shade[right color=yellow!60,left color=yellow!60](26,-3) rectangle(27,1);
\end{pgfonlayer}
\tablegrid
\end{tikztimingtable}
\end{document}
And output,
.
My problem is (like-3V) all in right voltages definitions flusright. How can I do?
