diff --git a/pt100/pt100.tex b/pt100/pt100.tex index f60baa6..fef2709 100644 --- a/pt100/pt100.tex +++ b/pt100/pt100.tex @@ -52,8 +52,6 @@ look-up tables or a suitable polynomial expression. \end{figure} - - The voltage ranges we expect from this three stage potential divider are shown in figure \ref{fig:pt100vrange}. Note that there is an expected range for each reading, for a given temperature span. @@ -155,52 +153,15 @@ on the effects of each test case are found in section \ref{pt100range} and \ref{pt100temp}. -\pagebreak -% \subsection{Single Fault Modes as PLD} -% -% The component~failure~modes in table \ref{ptfmea} can be represented as contours -% on a PLD diagram. Each test case, or analysis into the effects of the component failure -% caused by the component~failure is represented by an labelled asterisk. -% -% -% \begin{figure}[h] -% \centering -% \includegraphics[width=400pt,bb=0 0 518 365,keepaspectratio=true]{./pt100/pt100_tc.jpg} -% % pt100_tc.jpg: 518x365 pixel, 72dpi, 18.27x12.88 cm, bb=0 0 518 365 -% \caption{PT100 Component Failure Modes} -% \label{fig:pt100_tc} -% \end{figure} -% -% This circuit supplies two results, sense+ and sense- voltage readings. -% To establish the valid voltage ranges for these, and knowing our -% valid tempperature range for this example ({0\oc} .. {300\oc}) we can calculate -% valid voltage reading ranges by using the standard voltage divider equation \ref{eqn:vd} -% for the circuit shown in figure \ref{fig:vd}. - - -\begin{figure}[h] - \centering - \includegraphics[width=100pt,bb=0 0 183 170,keepaspectratio=true]{./pt100/voltage_divider.png} - % voltage_divider.png: 183x170 pixel, 72dpi, 6.46x6.00 cm, bb=0 0 183 170 - \caption{Voltage Divider} - \label{fig:vd} -\end{figure} -%The looking at figure \ref{fig:vd} the standard voltage divider formula (equation \ref{eqn:vd}) is used. - -\begin{equation} -\label{eqn:vd} - V_{out} = V_{in}.\frac{Z2}{Z2+Z1} -\end{equation} - \subsection{Range and PT100 Calculations} \label{pt100temp} PT100 resistors are designed to -have a resistance of \ohms{100} at 0 \oc \cite{eurothermtables}. +have a resistance of \ohms{100} at {0\oc} \cite{aoe},\cite{eurothermtables}. A suitable `wider than to be expected range' was considered to be {0\oc} to {300\oc} for a given application. According to the Eurotherm PT100 -tables \cite{eurothermtables}, this corresponded to the resistances \ohms{60.28} +tables \cite{eurothermtables}, this corresponded to the resistances \ohms{100} and \ohms{212.02} respectively. From this the potential divider circuit can be analysed and the maximum and minimum acceptable voltages determined. These can be used as bounds results to apply the findings from the @@ -246,48 +207,6 @@ Table \ref{ptbounds} gives ranges that determine correct operation. In fact it c for any single error (short or opening of any resistor) this bounds check will detect it. -%\vbox{ -%\subsubsection{Calculating Bounds: High Value : HP48 RPL} -% -% -%HP RPL calculator program to take pt100 resistance -%and convert to voltage and {\adctw} values. -% -%\begin{verbatim} -%<< -> p -% << -% p 2200 + 2200 2200 + p + / 5 * DUP 5 -% / 4096 * -% >> -%>> -%\end{verbatim} -%} -% -%\vbox{ -%\subsubsection{Calculating Bounds: LOW Value : HP48 RPL} -% -% -%HP RPL calculator program to take pt100 resistance -%and convert to voltage and {\adctw} values. -% -%\begin{verbatim} -%<< -> p -% << -% p 2200 2200 p 2200 + + / 5 * DUP 5 -% / 4096 * -% >> -%>> -%\end{verbatim} -%} -% -%\subsection{Implementation of Four Wire Circuit} -% -%A standard 4 wire PT100\cite[pp 992]{aoe} circuit is read by -%ports on the 12 bit ADC of the PIC18F2523\cite{pic18f2523}. -%Three readings are taken. A reading to confirm the voltage level -%over $R_2$ is taken, -%from which the current can be determined. -%The two sense lines then give the vo \section{Single Fault FMEA Analysis of PT100 Four wire circuit} @@ -312,7 +231,22 @@ This circuit supplies two results, sense+ and sense- voltage readings. To establish the valid voltage ranges for these, and knowing our valid temperature range for this example ({0\oc} .. {300\oc}) we can calculate valid voltage reading ranges by using the standard voltage divider equation \ref{eqn:vd} -for the circuit shown in . +for the circuit shown in figure \ref{fig:vd}. + + +\begin{figure}[h] + \centering + \includegraphics[width=100pt,bb=0 0 183 170,keepaspectratio=true]{./pt100/voltage_divider.png} + % voltage_divider.png: 183x170 pixel, 72dpi, 6.46x6.00 cm, bb=0 0 183 170 + \caption{Voltage Divider} + \label{fig:vd} +\end{figure} +%The looking at figure \ref{fig:vd} the standard voltage divider formula (equation \ref{eqn:vd}) is used. + +\begin{equation} +\label{eqn:vd} + V_{out} = V_{in}.\frac{Z2}{Z2+Z1} +\end{equation}