Error Message - Undefined control sequence

Question

I am using the Overleaf web site to put together an article, and this uses this code. I am getting the error I posted below and have not idea what to, any help would be great, not sure why even need to mess with code to do this! :/

Thanks!

Undefined control sequence.
\u-default-956 #1->\textmu 

l.31 ...Pressure mode with an aperture of 30.00 μ
                                                  m, and a voltage of 10 kV....

Answer 1

The error message tells you are using Unicode input encoding via package ucs and option utf8x of package inputenc. If you do not need ucs special features, then \usepackage[utf8]{inputenc} is the more common way.

The μ from the input is mapped to \textmu, which is not provided yet. Package textcomp provides it, for example, as suggested in Ruben's comment.

A more powerful way setting units is provided by package siunitx. It also takes care of the space between number and unit and prevents a line break between them.

\usepackage{siunitx}
\SI{30.00}{\micro\meter} ... \SI{10}{\kilo\volt}

Full example and my suggestion:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{siunitx}

\begin{document}
  Pressure mode with an aperture of \SI{30.00}{\micro\meter},
  and a voltage of \SI{10}{\kilo\volt} \dots
\end{document}

Or keeping units manually, keeping ucs and adding textcomp, the example would be:

\documentclass{article}
\usepackage{ucs}
\usepackage[utf8x]{inputenc}
\usepackage{textcomp}

\begin{document}
  Pressure mode with an aperture of 30.00\,μm,
  and a voltage of 10\,kV \dots
\end{document}

The \, sets a small non-breakable space, often set between the numbers and their units. The tilde ~ sets a normal non-breakable space.