power measurement intro + voltage ranges and disclaimer

glossaries.tex

@@ -52,6 +52,7 @@
 \newacronym{posix}{POSIX}{Portable operating system interface}
 \newacronym{MB}{MB}{Mega-Byte, unit of digital information}
 \newacronym{bsd}{BSD}{Berkeley Software Distribution}
+\newacronym{iec}{IEC}{International Electrotechnical Commission}
 
 
 \newglossaryentry{ethernet}{

problemexpres.tex

@@ -111,7 +111,7 @@ Wireless  & \gls {ieee}802.11n/g/b, \gls{ieee} 802.3, \gls{ieee} 802.3u \\
 
 
 \subsection{Atheros AR9331 wi-fi System-on-Chip}
-The Atheros AR9331 is a highly integrated and cost effective \gls{ieee} 802.11n 1x1 2.4 G\gls{hz} \gls{soc} for \gls{wlan} \gls{ap} and \gls{router} platforms. The block diagram of the chip can be seen on figure \ref{f:ar_block}. Features of this \gls{soc} are following:
+The Atheros AR9331 is a highly integrated and cost effective \gls{ieee} 802.11n 1x1 2.4 G\gls{hz} \gls{soc} for \gls{wlan} \gls{ap} and \gls{router} platforms. The block diagram of the chip can be seen in figure \ref{f:ar_block}. Features of this \gls{soc} are following:
 
 \begin{itemize}
 	\item Complete \gls{ieee} 802.11n 1x1 \gls{ap} or \gls{router} in a single chip
@@ -156,4 +156,38 @@ Whole printed circuit board of TL-WR703N was remade by the GL.inet team to expos
 \centering
 \includegraphics[width=.8\textwidth,angle=0]{gl-inet_pcb_down}
 \caption{The back side of the GL.inet board exposing the \Gls{flash} memory and a main voltage regulator}\label{f:board_back}
-\end{figure}
+\end{figure}
+
+
+
+
+\newpage
+\section{Electrical Power Measurements}
+Measuring the power makes most sense on the customer appliances. The first reason is, that they generally consume power that is purchased on contract. The energetic company measures all the power used up by the end customer, but customer has no easy way to see how much and how \textit{effectively} is power used by the appliances. The second important reason is that the appliances has a standardised connector (plug) that is guaranteed to fit in all the area using it, which is not a case for example on battery powered devices (batteries has different sizes, connectors and general properties.
+
+When it comes to measuring the electrical power, the first and the most important thing to discuss is safety. Only after all the safety precautions had been made clear, the theory can be clarified and subsequently, the practice can be applied. The chapter focuses solely on the first two topics.
+
+
+\subsection{Voltage ranges and safety disclaimer}
+The \gls{iec} international standard \textbf{IEC 60038:1983} defines a set of standard voltages for use in AC electricity supply systems.
+
+\begin{table}[ht!]
+\centering
+\caption{International standards grouping ranges of supply voltages to three categories}
+\label{t:volt_ranges}
+\tabcolsep=5pt 
+\renewcommand{\arraystretch}{1.3}
+\begin{tabular}{|l|l|l|l|}
+\hline
+{\bf IEC voltage range} & {\bf AC} & {\bf DC} & {\bf defining risk} \\ \hline
+High voltage & \textgreater 1000 V$_{rms}$ & \textgreater 1500 V & electrical arcing \\ \hline
+Low voltage & 50–1000 V$_{rms}$ & 120–1500 V & electrical shock \\ \hline
+Extra-low voltage & \textless 50 V$_{rms}$ & \textless 120 V & low risk \\ \hline
+\end{tabular}
+\end{table}
+
+The appliances under test work on mains voltage. In Europe, the nominal voltage of mains line for appliances is 230 V / 50 Hz. This falls into the voltage range, with defining risk of \textbf{electrical shock} as described in the table \ref{t:volt_ranges}.
+
+If not handled with care, operating or manipulating with voltage can cause permanent damage to appliance or health, or can cause fire or even death. Thus, respect, increased care and knowledge is necessary in all further practical steps involved.
+
+