ARRARARARRAGGHHHHH going mad

removing we from sentences. TORTURE
MENTAL TORTURE

mybib.bib

@@ -941,7 +941,6 @@ ISSN={1530-2059},}
   YEAR =         "1988"
 }
 
-
 @book{DBLP:books/ph/KernighanR88,
   author    = {Brian W. Kernighan and
                Dennis Ritchie},
@@ -1136,6 +1135,14 @@ ISSN={0098-5589},}
 }
  
 
+@MISC{microchipreliability,
+  author =       "Microchip",
+  title =        "Microchip: Reliability Data Search Engine: Annual Product Reliability Reports",
+ howpublished = "Microchip Inc. http://www.microchip.com/reliabilityreport/Default.aspx",
+  year =         "2013"
+}
+
+
 @MISC{javaarea,
   author =       "Sun~Micro~Systems",
   title =        "Java Area Operations",

submission_thesis/CH2_FMEA/copy.tex

@@ -24,11 +24,11 @@ are examined in the context of two sources of information that define failure mo
 To introduce the concept  of FMEA, a simple example is  given, using a hypothetical four to twenty milli-amp ({\ft}) %milli-amp 
 reader.
 %
-The four main current FMEA variants are described and we  develop %conclude by describing concepts
+The four main current FMEA variants are described %and we  develop %conclude by describing concepts
 the concepts
-that underlie the usage and philosophy of FMEA.
+that underlie the usage and philosophy of FMEA discussed.
 %
-We return to the overall process of FMEA and model it using UML. 
+The overall process of FMEA is then reviewed and modelled  using UML. 
 %
 By using UML  
 the entities needed to implement FMEA 
@@ -95,11 +95,12 @@ function that they perform.
 
 We begin FMEA with the basic, or starting components.
 %
-These components are the sort we buy in or consider as pre-assembled modules.
+These components are the sort bought in or considered as pre-assembled modules.
-We term these the {\bcs}; they are considered ``atomic'' i.e. they are not broken down further.
+These are termed {\bcs}; they are considered ``atomic'' i.e. they are not broken down further.
 %
-Firstly we need to know how these can fail, so our first relationship
+The first requirement for a {\bc} is to define the ways in which it can fail, 
-is between a {\bc} and its failure modes, see figure~\ref{fig:component_fm_rel}.
+this relationship %between a {\bc} and its failure modes, 
+is shown in figure~\ref{fig:component_fm_rel}.
 \fmmdglossBC
 %DIAGRAM of Base components and failure modes
 
@@ -114,8 +115,8 @@ is between a {\bc} and its failure modes, see figure~\ref{fig:component_fm_rel}.
 The next stage is analysis, that is reasoning applied to the system in the event of
 a given failure mode. 
 %
-To perform this we need to know how a failure
+To perform how a failure
-mode, considering its effect on other components in the system,
+mode, after considering its effect on other components in the system,
 will translate to a system level symptom/failure.
 %
 The result of FMEA  is to determine  system level failures, 
@@ -147,17 +148,23 @@ of this chapter.
 \fmmdglossBC
 \label{sec:determine_fms}
 \fmodegloss
-In order to apply any form of FMEA  we need to know the ways in which 
+In order to apply any form of FMEA  the ways in which 
-the {\bcs} we are using can fail. In practise, this part of the process is guided by
+the {\bcs}\footnote{A good introduction to hardware and software failure modes may be found in~\cite{sccs}[pp.114-124].} %used  
-the standards to which we are seeking to conform.% to.
+can fail must be clearly defined.
 %
-\footnote{A good introduction to hardware and software failure modes may be found in~\cite{sccs}[pp.114-124].}
+In practise, this part of the process is guided by
+the particular standard
+which is being conformed to. %we are seeking to conform.% to.
 %
-Typically, when choosing components for a design, we look at manufacturers' data sheets 
+Standards may differ in their definitions for the {\fms} of {\bcs}.
+The reasons for these differences are examined below using two example components. 
+%
+%
+Typically, when choosing components for a design, engineers will look at manufacturers' data sheets 
 which describe functionality, physical dimensions,
 environmental ranges, tolerances and by `reading~between~the~lines'
-in some cases can indicate how a component may fail/misbehave
+in some cases can indicate how a component may fail/misbehave.
-under given conditions.
+%under given conditions.
 %
 How %base 
 components could fail internally, is not of interest to an FMEA investigation.
@@ -168,8 +175,10 @@ A large body of literature exists giving guidance for the determination of  comp
 For this study FMD-91~\cite{fmd91} and the gas burner standard EN298~\cite{en298} are examined.
 %Some standards prescribe specific failure modes for generic component types.
 In EN298 failure modes for most generic component types are listed, or if not listed, 
-are determined using a procedure where we consider
+are determined using a procedure:
-all pins open and then all adjacent pins shorted.
+typically of the form of examining scenarios such as 
+`all~pins~open' and then `all~adjacent~pins~shorted'~\cite{en298}[A.1 note e]. 
+
 %a procedure where failure scenarios of all pins OPEN and all adjacent pins shorted 
 %are examined. 
 % 
@@ -185,9 +194,18 @@ component {\fms} suitable for use in FMEA.
 A third document, MIL-1991~\cite{mil1991} provides overall reliability statistics for 
 component types, but does not detail specific failure modes.
 %
-Using MIL1991 in conjunction with FMD-91 we can determine statistics for the failure modes
+Using MIL1991 in conjunction with FMD-91 statistics can be determined for the failure modes
 of component types. 
 %
+As these documents are now a little old, the results
+from them can be on the conservative side. 
+\frategloss
+\fmmdglossFIT
+%
+A FIT value for a micro-processor
+may be determined at around 100 using these documents for instance, but
+FIT claims for modern integrated micro-controllers are typically less than five~\cite{microchipreliability}.
+%
 The FMEA variant\footnote{EN61508 (and related standards) are based on the FMEA variant Failure Mode Effects and Diagnostic Analysis (FMEDA)}
 used for European standard EN61508~\cite{en61508} 
 requires statistics for Meantime to Failure (MTTF) for all {\bc} failure modes.
@@ -211,22 +229,25 @@ requires statistics for Meantime to Failure (MTTF) for all {\bc} failure modes.
 
 \section{Determining the failure modes of Components.}
 \fmodegloss
-The starting point in the  FMEA process  are the failure modes of the components 
+The starting points in the  FMEA process  are the failure modes of the {\bcs}.
-we would typically find in a production parts list, which we can term the {\bcs}.
+%s 
+%Typically found in a production parts list, which are termed the {\bcs}.
 %
-In order to define FMEA we must start with a discussion on how these failure modes are chosen.
+In order to define FMEA, a discussion on how these failure modes are defined and
+their relationship to particular standards is presented below.
 %
-In this section we pick %look in detail at 
+%In this section we pick %look in detail at 
-two common electrical components as examples, and examine how
+Two common electrical components are used as examples,
-the two chosen sources of {\fm} information define their failure mode behaviour.
+and examined against two sources of {\fm} information. % define their failure mode behaviour.
-We look at the reasons why some known failure modes % are omitted, or presented in 
-%specific but unintuitive ways.
-%We compare the US. military published failure mode specifications wi
-can be found in one source but not in the others and vice versa.
 %
-Finally we compare and contrast the failure modes determined for these components
+These definitions for a given generic component may not always agree.
+%
+The reasons why some {\fms} 
+can be found in one source but not in the others and vice versa, are discussed.
+%
+Finally the failure modes determined %for these components
 from the FMD-91~\cite{fmd91} reference source and from the guidelines of the 
-European burner standard EN298~\cite{en298}.
+European burner standard EN298~\cite{en298} are compared and contrasted.
 
 \subsection{Failure mode determination for generic resistor.}
 \label{sec:resistorfm}
@@ -238,14 +259,14 @@ The resistor is a ubiquitous component in electronics, and is therefore a good c
 %
 FMD-91\cite{fmd91}[3-178] lists many types of resistor
 and lists many possible failure causes.
-For instance for {\textbf{Resistor,~Fixed,~Film}} we are given the following failure causes:
+For instance for {\textbf{Resistor,~Fixed,~Film}} the following failure causes are given:
 \begin{itemize}
- \item Opened 52\%  
+ \item Opened 52\%  ,
-  \item Drift 31.8\%  
+  \item Drift 31.8\%  ,
- \item Film Imperfections 5.1\%  
+ \item Film Imperfections 5.1\%  ,
- \item Substrate defects 5.1\% 
+ \item Substrate defects 5.1\% ,
- \item Shorted 3.9\%  
+ \item Shorted 3.9\%  ,
- \item Lead damage 1.9\%  
+ \item Lead damage 1.9\%  .
 \end{itemize}
 % This information may be of interest to the manufacturer of resistors, but it does not directly
 % help a circuit designer.
@@ -253,27 +274,27 @@ For instance for {\textbf{Resistor,~Fixed,~Film}} we are given the following fai
 % against {\fms} that the resistor could exhibit.
 % We can determine these {\fms} by converting the internal failure descriptions
 % to {\fms} thus: 
-To make this useful for FMEA/FMMD we must assign each failure cause to symptomatic  failure mode descriptor
+To make this useful for FMEA/FMMD each failure cause must be mapped to a symptomatic failure mode descriptor
-as shown below.
+as listed below:
 %
 %and map these failure causes to three symptoms,
 %drift (resistance value changing), open and short.
 
 \begin{itemize}
- \item Opened 52\% $\mapsto$ OPENED
+ \item Opened 52\% $\mapsto$ OPENED,
-  \item Drift 31.8\% $\mapsto$ DRIFT
+  \item Drift 31.8\% $\mapsto$ DRIFT,
- \item Film Imperfections 5.1\% $\mapsto$ OPEN
+ \item Film Imperfections 5.1\% $\mapsto$ OPEN,
- \item Substrate defects 5.1\% $\mapsto$ OPEN
+ \item Substrate defects 5.1\% $\mapsto$ OPEN,
- \item Shorted 3.9\% $\mapsto$  SHORT
+ \item Shorted 3.9\% $\mapsto$  SHORT,
  \item Lead damage 1.9\% $\mapsto$ OPEN.
 \end{itemize}
 %
-We note that the main causes of resistor value drift are overloading. % of components.
+Note that the main causes of resistor value drift are overloading. % of components.
 This is borne out in the FMD-91~\cite{fmd91}[232] entry for a resistor network where the failure
 modes do not include drift.
 %
-If we can ensure that our resistors will not be exposed to overload conditions, the 
+If it is ensured that our resistors will not be exposed to overload conditions, the 
-probability of drift (sometimes called parameter change) occurring
+probability of drift (sometimes called parameter change) %occurring
 is significantly reduced, enough for some standards to exclude it~\cite{en298,en230}.
 
 
@@ -328,8 +349,8 @@ The differences in resistor failure modes between FMD-91 and EN298 are that FMD-
 include the failure mode DRIFT. EN298 does not include this, mainly because it imposes circuit design constraints
 that effectively side step that problem.
 %
-For this study we will take the conservative view from EN298, and consider the failure
+For this study the conservative view from EN298 is taken, and the failure
-modes for a generic resistor to be both OPEN and SHORT. We use the function $fm$ 
+modes for a generic resistor taken to be both OPEN and SHORT. The function $fm$ is used
 to return a set of failure modes,
 i.e.
 \label{ros}
@@ -348,7 +369,7 @@ $$ fm(R) = \{ OPEN, SHORT \} . $$
 The operational amplifier (op-amp) %is a differential amplifier and 
 is very widely used in nearly all fields of modern analogue electronics.
 %
-Only one of two sources of information on {\bc} {\fms} we are comparing
+Only one of two sources of information on {\bc} {\fms} being compared
 has an entry specific to operational amplifiers (FMD-91).
 %
 EN298 does not specifically define the 
@@ -358,16 +379,17 @@ components types not specifically listed in it.
 %
 Operational amplifiers are typically packaged in dual or quad configurations---meaning
 that a chip will typically contain two or four amplifiers.
-For the purpose of example for EN298, we look at
+%
+For the purpose of example for EN298, %we look at
 a typical op-amp designed for instrumentation and measurement, the dual packaged version of the LM358~\cite{lm358} 
-(see figure~\ref{fig:lm258}).
+(see figure~\ref{fig:lm258}) is examined.
 %
 With the results from both sources of {\fm} definition %
 %we compare 
 the failure mode definitions for FMD-91 and EN298 
 relating to operational amplifiers are compared.
 
-\paragraph{ Failure Modes of an Op-Amp according to FMD-91 }
+\paragraph{Failure Modes of an Op-Amp according to FMD-91.}
 \fmodegloss
 %Literature suggests, latch up, latch down and oscillation.
 For Op-Amp failures modes, FMD-91\cite{fmd91}{3-116] states,
@@ -382,38 +404,40 @@ Again these are mostly internal causes of failure, more of interest to the compo
 than a test engineer % designer 
 looking for the symptoms of failure.
 %
-We need to translate these failure causes within the Op-Amp into {\fms}.
+These failure causes within the Op-Amp need to be translated to symptomatic {\fms}.
 %
-We can look at each failure cause in turn, and map it to potential {\fms} suitable for use in FMEA
+Each failure cause  is examined in turn, and mapped to potential {\fms} suitable for use in FMEA
 investigations.
 
 \paragraph{Op-Amp failure cause: Poor Die attach.}
-The symptom for this is given as a low slew rate. This means that the op-amp
+The symptom for this is given as a low slew rate. 
-will not react quickly to changes on its input terminals.
+%
+This means that the op-amp will not react quickly to changes on its input terminals.
+%
 This is a failure symptom that may not be of concern in a slow responding system like an
 instrumentation amplifier. However, where higher frequencies are being processed,
 a signal may  be lost entirely.
-We can map this failure cause to a {\fm}, and we can call it $LOW_{slew}$.
+This failure cause can be mapped to a symptomatic {\fm} called $LOW_{slew}$.
 
 \paragraph{No Operation - over stress.}
 Here the OP-Amp has been damaged, and the output may be held HIGH or LOW, or may be 
 effectively tri-stated, i.e. not able to drive circuitry in along the next stages of 
-the signal path: we can call this state NOOP (no Operation).
+the signal path: this {\fm} is termed NOOP (no Operation).
 %
-We can map this failure cause to three {\fms}, $LOW$, $HIGH$, $NOOP$. 
+This failure cause thus maps to three {\fms}, $LOW$, $HIGH$, $NOOP$. 
 
 \paragraph{Shorted inputs: $V_+$  to $V_-$.}
 Due to the high intrinsic gain of an op-amp, and the effect of offset currents,
 this will force the output HIGH or LOW.
-We map this failure cause to $HIGH$ or $LOW$.
+This failure cause maps to $HIGH$ or $LOW$.
 
 \paragraph{Open input: $V_+$.}
 This failure cause will mean that the minus input will have the very high gain
 of the Op-Amp applied to it, and the output will be forced HIGH or LOW.
-We map this failure cause to $HIGH$ or $LOW$.
+This failure cause maps to $HIGH$ or $LOW$.
 
 \paragraph{Collecting Op-Amp failure modes from FMD-91.}
-We can define an Op-Amp, under FMD-91 definitions to have the following {\fms}.
+An Op-Amps' failure mode behaviour, under FMD-91 definitions will have the  following {\fms}.
 \begin{equation}
  \label{eqn:opampfms}
  fm(OpAmp) = \{ HIGH, LOW, NOOP, LOW_{slew} \}  
@@ -425,15 +449,20 @@ We can define an Op-Amp, under FMD-91 definitions to have the following {\fms}.
 EN298 does not specifically define  OP\_AMPS failure modes; these can be determined
 by following a  procedure for `integrated~circuits' outlined in
 annex~A~\cite{en298}[A.1 note e].
+%
 This demands that all open connections, and shorts between adjacent pins be considered as failure scenarios.
 We examine these failure scenarios on the dual packaged  $LM358$~\cite{lm358} %\mu741$  
 and determine its {\fms} in table ~\ref{tbl:lm358}.
-Collecting the op-amp failure modes from table ~\ref{tbl:lm358} we obtain the same {\fms}
+%
-that we got from FMD-91, listed in equation~\ref{eqn:opampfms}, except for
+% Collecting the op-amp failure modes from table ~\ref{tbl:lm358} we obtain the same {\fms}
+% that we got from FMD-91, listed in equation~\ref{eqn:opampfms}, except for
+% $LOW_{slew}$.
+%
+Collecting the op-amp failure modes from table ~\ref{tbl:lm358}  the same {\fms}
+that we got from FMD-91 are obtained---listed in equation~\ref{eqn:opampfms}---except for
 $LOW_{slew}$.
 
 
-
 %\paragraph{EN298: Open and shorted pin failure symptom determination technique}
 
 
@@ -636,11 +665,14 @@ Let us choose resistor R1 in the  OP-AMP gain circuitry.
    \item \textbf{F - Failures of given component} The resistor (R1) could fail by going OPEN or SHORT (EN298 definition).
     \item \textbf{M - Failure Mode} Consider the component failure mode SHORT
     \item \textbf{E - Effects} This will drive the minus input LOW causing a HIGH OUTPUT/READING
-   \item \textbf{A - Analysis} The reading will be out of the  normal range, and we will have an erroneous milli-volt reading
+   \item \textbf{A - Analysis} The reading will be out of the  normal range, i.e. will have an erroneous milli-volt reading
 \end{itemize}
 
 \fmeagloss
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%% WE removal project ends here today 08SEP2013                 %%%%%%%% 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 The analysis above has given us  a result for % one failure %scenario i.e.
 one single component failure mode.
@@ -649,8 +681,10 @@ for each failure mode of all the components in the system under investigation.
 %
 In theory we have had to look at the failure~mode
 in relation to the entire circuit. 
+%
 We have used intuition to determine the probable
 effect of this failure mode. 
+%
 For instance we have assumed that the resistor R1 going SHORT
 will not affect the ADC, the Microprocessor or the UART.
 %