From 7da9f75e2714bb1079dd03aabc94aceb29b5cf42 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Sat, 6 Nov 2010 12:11:58 +0000 Subject: [PATCH] Went through logic for test addition --- fmmd_design_aide/fmmd_design_aide.tex | 94 +++++++++++++++++++++++---- 1 file changed, 82 insertions(+), 12 deletions(-) diff --git a/fmmd_design_aide/fmmd_design_aide.tex b/fmmd_design_aide/fmmd_design_aide.tex index 700fcb5..98a56c4 100644 --- a/fmmd_design_aide/fmmd_design_aide.tex +++ b/fmmd_design_aide/fmmd_design_aide.tex @@ -216,7 +216,7 @@ We could detect the effect on the reading with the potential divider according to the following formula. %% check figures -The potential divider is now $\frac{820R+820R}{2M2+820R+820R}$ over 5V this gives +The potential divider is now $\frac{820R+820R}{2M2+820R+820R}$ over 5V ci this gives 3.724mV, amplified by 184 this is 0.685V \adcten{140}. % The potential divider with the second resistor @@ -257,9 +257,9 @@ can be switched on to apply the test parallel resistance, and off to obtain the correct reading. % We must examine each test case from these two perspectives. -For TEST LINE ON the transistor is turned OFF +For $\overline{TEST\_LINE}$ ON the transistor is turned OFF and we are in a test mode and expect the reading to go up by around \adcten{70}. -For TEST LINE OFF the tranistor is on and R36 is by-passed, +For $\overline{TEST\_LINE}$ OFF the tranistor is on and R36 is by-passed, and the reading is assumed to be valid. \begin{table}[h+] @@ -272,21 +272,91 @@ and the reading is assumed to be valid. % R & wire & res + & res - & description \hline \hline -%% OK TR1 OFF -TEST LINE ON & TC:1 $R36$ SHORT & No added resistance & NO TEST EFFECT & XX 1.38 \\ \hline -TEST LINE OFF & TC:1 $R36$ SHORT & dormant fault & NO SYMPTOM & XX 1.38 \\ \hline -TEST LINE ON & TC:2 $R36$ OPEN & open circuit & OPEN CIRCUIT & XX 12.42\\ \hline -TEST LINE OFF & TC:2 $R36$ OPEN & open circuit & OPEN CIRCUIT & XX 12.42\\ \hline +%% OK TR1 OFF , and so 36 in series. R36 has shorted so +$\overline{TEST\_LINE}$ ON & TC:1 $R36$ SHORT & No added resistance & NO TEST EFFECT & XX 1.38 \\ \hline +%% +$\overline{TEST\_LINE}$ OFF & TC:1 $R36$ SHORT & dormant failure & NO SYMPTOM & XX 1.38 \\ \hline +%% here TR1 should be OFF, as R36 is open we now have an open circuit +$\overline{TEST\_LINE}$ ON & TC:2 $R36$ OPEN & open circuit & OPEN CIRCUIT & XX 12.42\\ \hline +%% here TR1 should be ON and R36 by-passed, the fact it has gone OPEN means no symptom here, a dormant failure. +$\overline{TEST\_LINE}$ OFF & TC:2 $R36$ OPEN & dormant failure & NO SYMPTOM & XX 12.42\\ \hline \hline -TEST LINE ON & TC:3 $TR1$ ALWAYS ON & dormant fault & NO SYMPTOM & XX 1.38 \\ \hline -TEST LINE OFF & TC:3 $TR1$ ALWAYS ON & No added resistance & NO TEST EFFECT & XX 1.38 \\ \hline -TEST LINE ON & TC:4 $TR1$ ALWAYS OFF & resistance added failure & NO TEST EFFECT & XX 1.38 \\ \hline -TEST LINE OFF & TC:4 $TR1$ ALWAYS OFF & dormant fault & NO SYMPTOM & XX 1.38 \\ \hline +% +%% TR1 OFF so R36 should be in series. Because TR1 is ON because it is faulty, R36 is not in series +$\overline{TEST\_LINE}$ LINE ON & TC:3 $TR1$ ALWAYS ON & No added resistance & NO TEST EFFECT & XX 1.38 \\ \hline +%% +%% TR1 ON R36 should be bypassed by TR1, and it is, but as TR1 is always on we have a dormant failure. +$\overline{TEST\_LINE}$ OFF & TC:3 $TR1$ ALWAYS ON & dormant failure & NO SYMPTOM & XX 1.38 \\ \hline +%% +%% TR1 should be off as overline{TEST\_LINE}$ is ON. As TR1 is faulty it is always off and we have a dormant failure. +$\overline{TEST\_LINE}$ LINE ON & TC:4 $TR1$ ALWAYS OFF & dormant failure & NO SYMPTOM & XX 1.38 \\ \hline +%% +%% TR1 should be ON, but is off due to TR1 failure. The resistance R36 will always be in series therefore +$\overline{TEST\_LINE}$ OFF & TC:4 $TR1$ ALWAYS OFF & resistance always added & NO TEST EFFECT & XX 1.38 \\ \hline \hline \end{tabular} \label{tab:testaddition} \end{table} +\subsection{Test Cases Analysis in detail} + +The purpose of this circuit is to switch a resistance in when we want to test the circuit +and to switch it out for normal operation. +The control is provided by a line called $\overline{TEST\_LINE}$. +Thus to apply the test conditions we set $\overline{TEST\_LINE}$ to OFF or false +and to order normal operation we set it to ON or true. + +\subsubsection{TC 1} +This test case looks at the shorted resistor failure mode of R36. +\paragraph{$\overline{TEST\_LINE}$ ON} +Here TR1 should be off and R36 should be in series. As R36 is shorted, this means that +no resistance will be contributed to the circuit by R36. +In the terms of the behaviour +of the functional group, this means that it will provide no test effect. +\paragraph{$\overline{TEST\_LINE}$ OFF} +Here TR1 will be on and by-pass R36, so it does not make any difference if +R36 is shorted. This is a dormant failure, we can only detect this failure +when $\overline{TEST\_LINE}$ is ON. + + + +\subsubsection{TC 2} +This test case looks at the open circuit resistor failure mode of R36. +\paragraph{$\overline{TEST\_LINE}$ ON} +Here TR1 should be off and R36 should be in series. As R36 is open, this means that +the test circuit is no open. +In the terms of the behaviour +of the functional group, this means that it will cause an open circuit failure. +\paragraph{$\overline{TEST\_LINE}$ OFF} +Here TR1 will be on and by-pass R36, so it does not make any difference if +R36 is open. This is a dormant failure, we can only detect this failure +when $\overline{TEST\_LINE}$ is ON. + + +\subsubsection{TC 3} +This test case looks at the transistor failure mode where TR1 is always ON. +\footnote{The transistor is being used as a switch, and so we can model it as having two failure modes ALWAYS ON or ALWAYS OFF.} +\paragraph{$\overline{TEST\_LINE}$ ON} +Here TR1 should be off and R36 should be in series. As TR1 is always ON, this means that +R36 will always be by-passed. Thus there will be no test effect. +\paragraph{$\overline{TEST\_LINE}$ OFF} +Here TR1 should be on and by-pass R36. +This is a dormant failure, we can only detect this failure +when $\overline{TEST\_LINE}$ is ON. + +\subsubsection{TC 4} +This test case looks at the transistor failure mode where TR1 is always OFF. +\paragraph{$\overline{TEST\_LINE}$ ON} +Here TR1 should be OFF and R36 should be in series. +This is a dormant failure, we can only detect this failure +\paragraph{$\overline{TEST\_LINE}$ OFF} +Here TR1 should be ON, but is OFF due to failure. +The resistance R36 will always be in series. +As a symptom for this circuit, it means that there would be no test effect. + + +\subsection{conclusion of FMMD analysis on safety addition} + For the FMMD analysis in table \ref{tab:testaddition} we have two failure modes for its derived component `no~test~effect' or `open~circuit'. %~out~of~range'.