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Robin Clark 2010-10-07 19:37:03 +01:00
parent 4ac851a271
commit 4ec18c0321
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fmmd_design_aide/fmmd_design_aide.tex
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@ -76,7 +76,7 @@ We then analsye the {\fg} and the resultant {\dc} failure modes are discussed.
\begin{figure}[h] \begin{figure}[h]
\centering \centering
\includegraphics[width=200pt,bb=0 0 678 690,keepaspectratio=true]{./mv_opamp_circuit.png} \includegraphics[width=200pt,bb=0 0 678 690,keepaspectratio=true]{./fmmd_design_aide/mv_opamp_circuit.png}
% mv_opamp_circuit.png: 678x690 pixel, 72dpi, 23.92x24.34 cm, bb=0 0 678 690 % mv_opamp_circuit.png: 678x690 pixel, 72dpi, 23.92x24.34 cm, bb=0 0 678 690
\caption{Milli-Volt Amplifier with Safety/Offset Resistor} \caption{Milli-Volt Amplifier with Safety/Offset Resistor}
\label{fig:mv1} \label{fig:mv1}
@ -86,7 +86,7 @@ We then analsye the {\fg} and the resultant {\dc} failure modes are discussed.
This circuit amplifies a milli-volt input by a gain of $\approx$ 184 ($\frac{150E3}{820}+1$). This circuit amplifies a milli-volt input by a gain of $\approx$ 184 ($\frac{150E3}{820}+1$).
An offset is applied to the input by R18 and R22 forming a potential divider An offset is applied to the input by R18 and R22 forming a potential divider
of $\frac{820}{2.2E6+820}$. Will 5V applied as Vcc this gives an input offset of 1.86mV. of $\frac{820}{2.2E6+820}$. With 5V applied as Vcc this gives an input offset of 1.86mV.
So the amplified offset is $\approx 342mV$. We can determine the output of the amplifier So the amplified offset is $\approx 342mV$. We can determine the output of the amplifier
by subtracting this amount from the reading. We can also define an acceptable by subtracting this amount from the reading. We can also define an acceptable
range for the readings. This would depend on the milli-volt source, and also on the range for the readings. This would depend on the milli-volt source, and also on the