[Tex/LaTex] package sistyle and SIunits conflict, \micro already defined

errorssiunitssiunitx

I've got an error on my latex file when i use both package at the same time.
I haven't this error when i dont use one of the 2 package

 LaTeX Error: Command \micro already defined.

 Or name \end... illegal, see p.192 of the manual.

 See the LaTeX manual or LaTeX Companion for explanation.
 Type  H <return>  for immediate help.
  ...                                              

 l.609 \begin{document}

 Your command was ignored.
 Type  I <command> <return>  to replace it with another command,
 or  <return>  to continue without it.

But if I don't use the SIUnits package I got errors on these commands:

\ampere
\ohm
\degreecelsius
\volt
\mega \ohm
\milli \ohm
\kelvin

And when I dont use sistyle package I got errors on these commands 

\num*
\sqrt \num*

Here is the small example:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{comment}
\usepackage[english]{babel}
\usepackage{geometry}
\usepackage{chemist}      
\usepackage{etex}
\usepackage{expl3}
\usepackage[version=4]{mhchem}
\usepackage{tikz}
\usetikzlibrary{circuits.ee.IEC}
\usepackage[european]{circuitikz}
\usepackage{sistyle}
\usepackage{SIunits}
\usepackage{url}
\usepackage{hyperref}
\usepackage{graphicx}
\usepackage{calc}
\usepackage{color}

%
%

\begin{document}

THIS IS A TEST
\end{document}

Can you help me

Thank you

Jules

Best Answer

change order how you load packages in preamble to:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{comment}
\usepackage[english]{babel}
\usepackage{geometry}
\usepackage{chemist}
%\usepackage{etex} it is some years default
\usepackage{expl3}
\usepackage[version=4]{mhchem}
\usepackage{tikz}
\usetikzlibrary{circuits.ee.IEC}
\usepackage[european]{circuitikz}
\usepackage{SIunits}
\usepackage{sistyle}
\usepackage{graphicx}
\usepackage{calc}
\usepackage{color}
\usepackage{url}
\usepackage{hyperref}

\begin{document}

THIS IS A TEST
\end{document}

however, you should consider to use siunitx and changes used units names accordingly (by help of editor find-replace function) and drop SIunits and sistyle.

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