127 lines
4.0 KiB
TeX
127 lines
4.0 KiB
TeX
%
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% Make the revision and doc number macro's then they are defined in one place
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\ifthenelse {\boolean{paper}}
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{
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\begin{abstract}
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This paper looks in detail a the generic `resistor'
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as a component in safety critical designs and
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how its potential failure modes are taken into
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account in various safety design standards.
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A `networked resistor' equivalent to single
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resistors is proposed for highly safety critical measurement sensitive
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designs, as it has two not three failure modes to consider.
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\end{abstract}
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}
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{
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\section{Overview}
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Component failure modes are documented for most generic
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components~\cite{mil1992}~\cite{rac}. There are some differences in
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the failure modes that we are required to consider for various
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safety standards.
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For an example of this we can look in detail at one particular
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type
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of component, and examine potential causes of failure modes and
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and how various standards demands in terms of possible failure modes.
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For this study the common resistor ahs been chosen.
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}
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\section{Resistor Failure Modes}
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Most common failure OPEN
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ENXXX ays only consider OPEN
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EN298 considers OPEN and SHORT
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\subsection{Physical causes for a resristor short}
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* over heating causing a solder bridge
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* over heating causing the component to melt and short (wirewound)
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\subsection{Physical causes for a resristor open}
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* Over current causing the component to burn out (acting like a fuse).
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* vacuum conditions can cause solder joints to sublime (space ref jbis)
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\subsection{Physical causes for a resristor parameter change}
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*the resistor can react to over heating by becoming
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damaged so that the resistance track is internally shorted, making the
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part read a lower resistance
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*the resistor can over heat and the resistance track and be made thinner leading to a higher resistance
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*chemical attack could alter the properties of the resistance track.
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*RAC give parameter change as well
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this means that the resistor may change its resistance value
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as a failure mode.
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\section{Properties of a resistor network}
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RAC gives a resistor network
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as having only failure modes of
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OPEN and SHORT.
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Let us consider a simple resistoir network.
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Examine all causes.
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Assume resistors not from same batch.
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Show how parameter change is cancelled out, use sum of squares statistics
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to show by how much.
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\ifthenelse {\boolean{paper}}
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{
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\begin{figure}
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\begin{tikzpicture}[line width=1pt]
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\draw (0,0) -- ++(0,1cm);
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\draw[decorate, decoration=cell] (0,1cm) -- ++(0,1.5cm);
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\draw (0,2.5cm) |- ++(1cm,1cm);
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\draw[decorate, decoration=diode] (1cm,3.5cm) -- ++(1.5cm,0);
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\draw (2.5cm,3.5cm) -- ++(2,0);
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\draw (3.5cm,3.5cm) -- ++(0,-1);
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\draw[decorate, decoration=switch] (3.5cm,2.5cm) -- ++(0,-1.5cm);
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\draw[decorate,
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decoration={inductor,amplitude=0.35cm, segment length=0.75cm}]
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(4.5cm,3.5cm) -- ++(1.5cm,0);
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\draw (6cm,3.5cm) -- ++(1,0);
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\draw (7cm,3.5cm) -- ++(3,0);
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\draw (8cm,3.5cm) -- ++(0,-1);
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\draw[decorate, decoration=capacitor] (8cm,2.5cm) -- ++(0,-1.5cm);
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\draw (0cm,0cm) -| ++(8cm,1cm);
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\draw (3.5cm,0cm) -- ++(0cm,1cm);
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\draw (10cm,3.5cm) -- ++(0,-1);
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\draw[decorate, decoration=recresistor] (10cm,2.5cm) -- ++(0,-1.5cm);
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%\draw[decorate, decoration=recresistor] (2.5cm,10cm) -- ++(0,-1.5cm);
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\draw (8cm,0cm) -| ++(2cm,1cm);
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\draw[decorate, decoration=ground] (5,0cm) -- ++(0,-1.5cm);
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\end{tikzpicture}
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\caption{a circuit}
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\end{figure}
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\begin{figure}
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\begin{tikzpicture}[line width=1pt]
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\draw (0,0) -- ++(1cm,1cm);
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\draw[decorate, decoration=recresistor] (1cm,2cm) -- ++(0,-1.5cm);
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\draw[decorate, decoration=recresistor] (2cm,2cm) -- ++(0,-1.5cm);
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\draw[decorate, decoration=recresistor] (1cm,4cm) -- ++(0,-1.5cm);
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\draw[decorate, decoration=recresistor] (2cm,4cm) -- ++(0,-1.5cm);
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%\draw[decorate, decoration=recresistor] (2.5cm,10cm) -- ++(0,-1.5cm);
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\draw (8cm,0cm) -| ++(2cm,1cm);
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\draw[decorate, decoration=ground] (5,0cm) -- ++(0,-1.5cm);
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\end{tikzpicture}
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\caption{A `network resistor'}
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\end{figure}
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}
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{
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electComp not in main thesis director yet
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}
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