From 2f17ed2ec883f1210fd9b247e09458af8647e1e0 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Wed, 18 Sep 2013 08:57:39 +0100 Subject: [PATCH] CH5 AF comments --- submission_thesis/CH2_FMEA/copy.tex | 3 +++ submission_thesis/CH5_Examples/copy.tex | 25 ++++++++++++++----------- 2 files changed, 17 insertions(+), 11 deletions(-) diff --git a/submission_thesis/CH2_FMEA/copy.tex b/submission_thesis/CH2_FMEA/copy.tex index 8e9d5f0..5bca417 100644 --- a/submission_thesis/CH2_FMEA/copy.tex +++ b/submission_thesis/CH2_FMEA/copy.tex @@ -429,8 +429,11 @@ investigations. \fmmdglossOPAMP The symptom for this is given as a low slew rate. % +Slew rate for a circuit/component is the rate at which it changes an output voltage level (i.e. $\frac{\delta V}{\delta t} $). +% This means that the op-amp will not react quickly to changes on its input terminals. % +% This is a failure symptom that may not be of concern in a slow responding system like an instrumentation amplifier. However, where higher frequencies are being processed, a signal may be lost entirely. diff --git a/submission_thesis/CH5_Examples/copy.tex b/submission_thesis/CH5_Examples/copy.tex index 6baa7e7..7b8d365 100644 --- a/submission_thesis/CH5_Examples/copy.tex +++ b/submission_thesis/CH5_Examples/copy.tex @@ -78,9 +78,7 @@ A valid range for the output value of this circuit is assumed. %and voltages higher than a given threshold considered as HIGH. % Because the amplifier inverts and the input is guaranteed positive any -output voltage above or equal to zero would be erroneous. -% -This would be an `$AMP_{HIGH}$' failure symptom. +output voltage above or equal to zero would be erroneous i.e. an `$AMP_{HIGH}$' failure symptom. % A threshold would be determined for an `$AMP_{LOW}$' failure symptom (i.e. the output voltage more negative than expected). % error given the expected input range. % @@ -183,7 +181,8 @@ The final stage of analysis for this amplifier, is made by by forming a {\fg} with the OpAmp and the new {\dc} $IPD$. % \begin{table}[h+] -\caption{Inverting Amplifier: Single failure analysis using the $PD$ {\dc}} +\centering +\caption{Inverting Amplifier: Single failure analysis using the $IPD$ {\dc}} \begin{tabular}{|| l | l | c | c | l ||} \hline %\textbf{Failure Scenario} & & \textbf{Inverted Amp Effect} & & \textbf{Symptom} \\ \hline \textbf{Failure} & & \textbf{Inverted Amp. Effect} & & \textbf{Symptom} \\ @@ -460,7 +459,10 @@ This means R3 R4 is not a fixed potential divider, with R4 being on the positive % It could be at either polarity. % (i.e. the other way around R4 could be the negative side). % -Here it is more intuitive to model the resistors not as a potential divider, but individually. +Here, even though R3 and R4 are used as a potential divider, +it could be either inverted or non-inverted according to the voltages on the inputs. +Therefore the resistors cannot modelled as a potential divider, but must be placed in the {\fg} +with the OpAmp and analysed. %This means we are either going to %get a high or low reading if R3 or R4 fail. @@ -661,6 +663,7 @@ The first order low pass filter is analysed in table~\ref{tbl:firstorderlpass}.\ \begin{table}[h+] +\centering \caption{FirstOrderLP: Failure Mode Effects Analysis: Single Faults} % title of Table \label{tbl:firstorderlpass} @@ -821,7 +824,7 @@ and these are marked on the circuit schematic in figure~\ref{fig:circuit2002_FIV \label{fig:circuit2002_FIVEPOLE} \end{figure} % -\pagebreak[4] +%\pagebreak[4] % So the final {\fg} will consist of the derived components $\{ LP1, SKLP_1, SKLP_2 \}$. % @@ -1214,7 +1217,7 @@ increases the potential for re-use. % of pre-analysed {\dcs}. % A finer grained model---with potentially more hierarchy stages---also means that %more work, or -more reasoning stages have been used in the analysis. +more reasoning stages, i.e. FMMD analysis stages with their associated analysis reports, have been used in the analysis. % HTR The more we can modularise, the more we decimate the $O(N^2)$ effect % HTR of complexity comparison. % @@ -1227,7 +1230,7 @@ However, it involves a large reasoning distance, the final stage having 24 failure modes to consider against each of the other seven {\dcs}. A finer grained approach produces more potentially re-usable {\dcs} and involves several stages with lower reasoning distances. -The lower reasoning distances, or complexity comparision figures are given in the metrics chapter~\ref{sec:chap7} +The lower reasoning distances, or complexity comparison figures are given in the metrics chapter~\ref{sec:chap7} at section~\ref{sec:bubbaCC}. These show that the finer grained models also benefit from lower reasoning distances for the failure mode model. @@ -1731,7 +1734,7 @@ expected voltages for failure mode and temperature reading purposes. \begin{equation} \label{eqn:vd} - V_{out} = V_{in}.\frac{Z2}{Z2+Z1} + V_{out} = V_{in}.\frac{Z_2}{Z_2+Z_1} \end{equation} \subsection{Safety case for 4 wire circuit: Detailed calculations} @@ -1843,8 +1846,8 @@ As the voltage over $R_3$ is relative (a design feature to eliminate resistance the current can be calculated by reading the voltage over the known resistor $R2$.\footnote{To calculate the resistance of the Pt100 we need the current flowing though it. -This can be determined via Ohms law applied to $R_2$, $V=IR$, $I=\frac{V}{R_2}$, -and then using $I$, with $I$, $R_{3} = \frac{V_{R3}}{I}$.} +This can be determined via Ohms law applied to $R_2$, $V=I R_2$, $I=\frac{V}{R_2}$, +and then using $I$, $R_{3} = \frac{V_{R3}}{I}$.} As these calculations are performed by Ohms law, which is linear, the accuracy of the reading will be determined by the accuracy of $R_2$ and $R_{3}$. %It is reasonable to