ref to voltage divider

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Robin 2010-03-24 10:46:00 +00:00
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@ -52,8 +52,6 @@ look-up tables or a suitable polynomial expression.
\end{figure} \end{figure}
The voltage ranges we expect from this three stage potential divider The voltage ranges we expect from this three stage potential divider
are shown in figure \ref{fig:pt100vrange}. Note that there is are shown in figure \ref{fig:pt100vrange}. Note that there is
an expected range for each reading, for a given temperature span. 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}. 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} \subsection{Range and PT100 Calculations}
\label{pt100temp} \label{pt100temp}
PT100 resistors are designed to 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} A suitable `wider than to be expected range' was considered to be {0\oc} to {300\oc}
for a given application. for a given application.
According to the Eurotherm PT100 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 and \ohms{212.02} respectively. From this the potential divider circuit can be
analysed and the maximum and minimum acceptable voltages determined. analysed and the maximum and minimum acceptable voltages determined.
These can be used as bounds results to apply the findings from the 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 for any single error (short or opening of any resistor) this bounds check
will detect it. 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} \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 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 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} 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}