image { } problem

Question

\def \mic {\unit{\micro\meter}}

\begin{figure}[h]

\includegraphics[scale=0.8]{C:/Users/21_12_test10}

\caption[6 nozzles working in parallel at 40V with 20~\mic drop spacing.]{6 nozzles working in parallel at 40V with 20~\mic drop spacing.\newline
top row images: line widths of 158 - 170 - 160 - 173~\mic ;\newline bottom row images: uniform spacings of 109 - 71 - 74~\mic}

\label{IJ_2_8}

\end{figure}

I other image with similar syntax in the same folder work completely correct, but with this one I always get:

! Missing } inserted.
<inserted text>
}
l.1399 ...e widths of 158 - 170 - 160 - 173~\mic }
; \newline bottom row imag...
I've inserted something that you may have forgotten.
(See the <inserted text> above.)
With luck, this will get me unwedged. But if you
really didn't forget anything, try typing `2' now; then
my insertion and my current dilemma will both disappear.
! Missing } inserted.
<inserted text>
}

I really do not know whats meant by "try typing 2 now"? where do I type this?

Answer 1

I don't know in which package \unit is defined, given the absence of a complete example. But declaring new units/short hand units is easy with siunitx package.

Code:

\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage{siunitx}
\DeclareSIUnit{\mic}{\micro\meter} %% declare a new unit
\begin{document}
\noindent
 {\small
\begin{tabular}{lll}
 \verb|12\si{\mic}|                    & : & 12\si{\mic}                    \\ %% this is how we use it or
 \verb|\SI{12}{\mic}|                  & : & \SI{12}{\mic}                  \\ %% or
 \verb|\SIrange{10}{20}{\mic}|         & : & \SIrange{10}{20}{\mic}         \\ %% or
 \verb|\SIlist{158;170;160;173}{\mic}| & : & \SIlist{158;170;160;173}{\mic} \\ 
 \verb|\SIlist{109;71;74}{\mic}|       & : & \SIlist{109;71;74}{\mic}                          
\end{tabular} 
}

\begin{figure}[h]

\includegraphics[scale=0.8]{C:/Users/21_12_test10}

\caption[6 nozzles working in parallel at 40V with 20\si{\mic} drop spacing.]{\parbox[t]{.86\textwidth}{6 nozzles working in parallel at 40V with 20\si{\mic} drop spacing. \\
top row images: line widths of \SIlist{158;170;160;173}{\mic} ; \\
bottom row images: uniform spacings of \SIlist{109;71;74}{\mic}}}

\label{IJ_2_8}

\end{figure}
\end{document}

Edit:

To answer the comment by OP:

The command \unit should be used like: \unit{120}{\kilo\meter\per\hour} according to the documentation. Hence the definition \def \mic {\unit{\micro\meter}} proves to be wrong. Instead use something like: \newcommand*{\mic}[1]{\unit{#1}{\micro\meter}}

\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage[Gray,squaren,thinqspace,thinspace]{SIunits}
%\def\mic{\micro\meter}
\newcommand*{\mic}[1]{\unit{#1}{\micro\meter}}

\begin{document}
\begin{figure}[h]

\includegraphics[scale=0.8]{C:/Users/21_12_test10}

\caption[6 nozzles working in parallel at 40V with \mic{20}\ drop spacing.]{6 nozzles working in parallel at 40V with \mic{20} drop spacing.\newline
top row images: line widths of 158 - 170 - 160 - \mic{173} ;\newline bottom row images: uniform spacings of 109 - 71 - \mic{74}}

\label{IJ_2_8}

\end{figure}
\end{document}

Answer 2

EDIT: using the xspace package, you can define your command with \xspace (see the adapted example), which will recognize whether there needs to be a space after the command or not.

Here to give you a working example:

\documentclass{article}
\usepackage{graphicx}
\usepackage{SIunits}
\usepackage{xspace}
\newcommand{\mic}{\micro\meter\xspace}

\begin{document}

\begin{figure}[h]
\includegraphics[scale=0.8]{texlogo}
\caption{6 nozzles working in parallel at 40V with 20\mic drop spacing.\newline
top row images: line widths of 158 - 170 - 160 - 173\mic;
\newline bottom row images: uniform spacings of 109 - 71 - 74\mic}
\label{IJ_2_8}
\end{figure}

\end{document}

Giving you: