From 770c27d88fa640d1bef2b984d46ade5ef7f997c4 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Fri, 18 Jun 2010 08:45:22 +0100 Subject: [PATCH] refs + comments --- pt100/pt100.tex | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/pt100/pt100.tex b/pt100/pt100.tex index 4ef2022..90b0797 100644 --- a/pt100/pt100.tex +++ b/pt100/pt100.tex @@ -807,7 +807,8 @@ in figure \ref{fig:dubsim}. \clearpage \subsection{Derived Component : The PT100 Circuit} The PT100 circuit again, can now be treated as a component in its own right, and has two failure modes, -{\textbf{OUT\_OF\_RANGE}} and {\textbf{FLOATING}}. It can now be represented as a PLD see figure \ref{fig:pt100_doublef}. +{\textbf{OUT\_OF\_RANGE}} and {\textbf{FLOATING}}. +It can now be represented as a PLD see figure \ref{fig:pt100_doublef}. \begin{figure}[h] \centering @@ -819,6 +820,13 @@ The PT100 circuit again, can now be treated as a component in its own right, and \subsection{Statistics} +%% +%% Need to talk abou the `detection time' +%% or `Safety Relevant Validation Time' ref can book +%% EN61508 gives detection calculations to reduce +%% statistical impacts of failures. +%% + If we consider the failure modes to be statistically independent we can calculate the FIT values for all the failures. The failure mode of concern, the undetectable {\textbf{FLOATING}} condition requires that resistors $R_1$ and $R_2$ fail. We can multiply the MTTF