finish off detailed double analysis
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pt100/pt100.tex
143
pt100/pt100.tex
@ -24,7 +24,6 @@ from an FMEA persepective as a component itself, with a set of known failure mod
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\end{abstract}
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\end{abstract}
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}
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}
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{
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{
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\section{Overview}
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\section{Overview}
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The PT100, or platinum wire \ohms{100} sensor is
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The PT100, or platinum wire \ohms{100} sensor is
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a widely used industrial temperature sensor that is
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a widely used industrial temperature sensor that is
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@ -43,8 +42,6 @@ the failure modes of the components, analysing the circuit using FMEA
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and producing a failure mode model for the circuit as a whole.
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and producing a failure mode model for the circuit as a whole.
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Thus after the analysis the PT100 temperature sensing circuit, may be veiwed
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Thus after the analysis the PT100 temperature sensing circuit, may be veiwed
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from an FMEA persepective as a component itself, with a set of known failure modes.
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from an FMEA persepective as a component itself, with a set of known failure modes.
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}
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}
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\begin{figure}[h]
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\begin{figure}[h]
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@ -271,6 +268,7 @@ and are thus enclosed by one contour each.
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\label{fig:pt100_tc}
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\label{fig:pt100_tc}
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\end{figure}
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\end{figure}
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ating input Fault
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This circuit supplies two results, sense+ and sense- voltage readings.
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This circuit supplies two results, sense+ and sense- voltage readings.
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To establish the valid voltage ranges for these, and knowing our
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To establish the valid voltage ranges for these, and knowing our
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valid temperature range for this example ({0\oc} .. {300\oc}) we can calculate
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valid temperature range for this example ({0\oc} .. {300\oc}) we can calculate
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@ -566,8 +564,143 @@ conditions.
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\clearpage
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\clearpage
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\section{ PT100 Double Simultaneous \\ Fault Analysis}
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\section{ PT100 Double Simultaneous \\ Fault Analysis}
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In this section we examine the failure mode behaviour for all single
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faults and double simultaneous faults.
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This corresponds to the cardinality contstrained powerset of
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the failure modes in the functional group.
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All the single faults have already be proved in the last section.
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For the next set of test cases, let us again hypothesise
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the failure modes, and then examine each one in detail with
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potential divider equation proofs.
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Table \ref{tab:ptfmea2} lists all the combinations of double
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faults and then hypothesises how the functional~group will react
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under those conditions.
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\begin{table}[ht]
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\caption{PT100 FMEA Double Faults} % title of Table
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\centering % used for centering table
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\begin{tabular}{||l|l|c|c|l|l||}
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\hline \hline
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\textbf{TC} &\textbf{Test} & \textbf{Result} & \textbf{Result } & \textbf{General} \\
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\textbf{number} &\textbf{Case} & \textbf{sense +} & \textbf{sense -} & \textbf{Symtom Description} \\
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% R & wire & res + & res - & description
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\hline
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\hline
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TC 7: & $R_1$ OPEN $R_2$ OPEN & Floating input Fault & Floating input Fault & Unknown value readings \\ \hline
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TC 8: & $R_1$ OPEN $R_2$ SHORT & low & low & Both out of range \\ \hline
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\hline
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TC 9: & $R_1$ OPEN $R_3$ OPEN & high & low & Both out of Range \\ \hline
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TC 10: & $R_1$ OPEN $R_3$ SHORT & low & low & Both out of range \\ \hline
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\hline
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TC 11: & $R_1$ SHORT $R_2$ OPEN & high & high & Both out of range \\ \hline
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TC 12: & $R_1$ SHORT $R_2$ SHORT & high & low & Both out of range \\ \hline
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\hline
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TC 13: & $R_1$ SHORT $R_3$ OPEN & high & low & Both out of Range \\ \hline
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TC 14: & $R_1$ SHORT $R_3$ SHORT & high & high & Both out of range \\ \hline
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\hline
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TC 15: & $R_2$ OPEN $R_3$ SHORT & high & Floating input Fault & sense+ out of range \\ \hline
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TC 16: & $R_2$ OPEN $R_3$ SHORT & high & high & Both out of Range \\ \hline
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TC 17: & $R_2$ SHORT $R_3$ OPEN & high & low & Both out of Range \\ \hline
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TC 18: & $R_2$ SHORT $R_3$ SHORT & low & low & Both out of Range \\ \hline
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\hline
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\end{tabular}
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\label{tab:ptfmea2}
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\end{table}
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\subsection{Verifying complete coverage for a \\ cardinality constrained powerset of 2}
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It is important to check that we have covered all possible double fault combinations.
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We can use the equation \ref{eqn:correctedccps2}, reproduced below to verify this.
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DO THE DOUBLE
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% typeset in {\Huge \LaTeX} \today
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\begin{equation}
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|{\mathcal{P}_{cc}SU}| = {\sum^{k}_{1..cc} \frac{|{SU}|!}{k!(|{SU}| - k)!}}
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- \sum^{p}_{2..cc}{{\sum^{j}_{j \in J} \frac{|FM({C_j})|!}{p!(|FM({C_j})| - p)!}} }
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\label{eqn:correctedccps2}
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\end{equation}
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$|FM(C_j)|$ is always 2 here, as all the components are resistors and have two failure modes.
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%
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% Factorial of zero is one ! You can only arrange an empty set one way !
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Populating this equation with $|SU| = 6$ and $|FM(C_j)|$ is always 2 here as all the components are resistors and have two failure modes.
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\begin{equation}
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|{\mathcal{P}_{2}SU}| = {\sum^{k}_{1..2} \frac{6!}{k!(6 - k)!}}
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- \sum^{p}_{2..2}{{\sum^{j}_{1..3} \frac{2!}{p!(2 - p)!}} }
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\label{eqn:correctedccps2}
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\end{equation}
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$|{\mathcal{P}_{2}SU}|$ is the number of valid combinations of faults to check
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under the conditions of unitary state failure modes for the components (a resistor cannot fail by being shorted and open at the same time).
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Expanding the sumations
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$$ NoOfTestCasesToCheck = \frac{6!}{1!(6-1)!} + \frac{6!}{2!(6-2)!} - \Big( \frac{2!}{2!(2 - 2)!} + \frac{2!}{2!(2 - 2)!} + \frac{2!}{2!(2 - 2)!} \Big) $$
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$$ NoOfTestCasesToCheck = 6 + 15 - ( 1 + 1 + 1 ) = 18 $$
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As the test case are all different and are of the correct cardinalities (6 single faults and (15-3) double)
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we can be confident that we have looked at all combinations up to two, of the possible faults
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in the pt100 circuit. The next task is to investigate
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these test cases in more detail to prove the failure mode hypothese set out in table \ref{tab:ptfmea2}.
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\subsection{Proof of Double Faults Hypothese }
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\subsubsection{ TC 7 : Voltages $R_1$ OPEN $R_2$ OPEN }
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This double fault mode produces an interesting symptom.
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Both sense lines are floating.
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We cannot know what the {\adctw} readings on them will be.
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In practise these would probably float to low values
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but for the purpose of a safety critical analysis
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all we can say is the values are `floating' and `unknown'.
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This is an interesting case, because it is, at this stage an undetectable
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fault that must be handled.
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\subsubsection{ TC 8 : Voltages $R_1$ OPEN $R_2$ SHORT }
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This cuts the supply from Vcc. Both sense lines will be at zero.
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Thus both values will be out of range.
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\subsubsection{ TC 9 : Voltages $R_1$ OPEN $R_3$ OPEN }
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Sense- will be floating.
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Sense+ will be tied to Vcc and will thus be out of range.
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\subsubsection{ TC 10 : Voltages $R_1$ OPEN $R_3$ SHORT }
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This shorts ground to the
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both of the sense lines.
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Both values thuis out of range.
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\subsubsection{ TC 11 : Voltages $R_1$ SHORT $R_2$ OPEN }
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This shorts both sense lines to Vcc.
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Both values will be out of range.
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\subsubsection{ TC 12 : Voltages $R_1$ SHORT $R_2$ SHORT }
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This shorts the sense+ to Vcc and the sense- to ground.
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Both values will be out of range.
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typeset in {\Huge \LaTeX} \today
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@ -4,29 +4,37 @@
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\ifthenelse {\boolean{paper}}
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\ifthenelse {\boolean{paper}}
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{
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{
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\begin{abstract}
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\begin{abstract}
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This chapter describes the legal frameworks and standards organisations
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This paper describes the legal frameworks and standards organisations
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that exist in Europe and North America.
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that exist in Europe and North America.
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Some specific standards (that the author has experience with directly)
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Some specific standards (that the author has experience with directly)
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are reviewed.
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are reviewed.
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\end{abstract}
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\end{abstract}
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}
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}
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{}
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{
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This chapter describes the legal frameworks and standards organisations
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that exist in Europe and North America.
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Some specific standards (that the author has experience with directly)
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are reviewed.
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}
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\section{Introduction}
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\section{Introduction}
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\subsection{Product Life Cycle}
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\subsection{Product Life Cycle}
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i
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difffernent areas
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difffernent areas
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EN61508 REQ to SPEC to DESIGN
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EN61508 REQ to SPEC to DESIGN
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EN298
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EN298
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DESIGN TO PRODUCT
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DESIGN TO
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TESTING (EMC PRODUCT
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FM
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FM
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PRODUCT VERIFICATION MONITORING
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PRODUCT VERIFICATION MONITORING
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NEW A PRODUCT LIFE CYCLE IMAGE WITH AN EULER DIAGRMA FOR THE DIFFERENT STANDARDS
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Different agencies - approval is testing of new product
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Different agencies - approval is testing of new product
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and verification to standard - manufacturing overwatch / supervision
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and verification to standard - manufacturing overwatch / supervision
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word on tip of tounge -
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word on tip of tounge -
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