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Robin Clark 2011-02-21 16:53:31 +00:00
parent 91f2923e38
commit ee1a2397f7
1 changed files with 3 additions and 3 deletions
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pt100/pt100.tex
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@ -280,8 +280,8 @@ by separate wires and the resistance in those are effectively cancelled
out by considering the voltage reading over $R_3$ to be relative.
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The PT100 element is a precision part and will be chosen for a specified accuracy/tolerance range.
One or other of the load resistors (the one we measure current over) should also
be of this accuracy.
One or other of the load resistors (the one we measure current over) should
be of a specified accuracy.
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The \ohms{2k2} loading resistors should have a good temperature co-effecient
(i.e. $\leq \; 50(ppm)\Delta R \propto \Delta \oc $).
@ -297,7 +297,7 @@ We can determine this via ohms law applied to $R_2$, $V=IR$, $I=\frac{V}{R_2}$,
and then using $I$, we can calculate $R_{3} = \frac{V_{3}}{I}$.} and then use ohms law again to calculate
the resistance of $R_3$.
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As these calculations are performed by ohms law, the accuracy of the reading
As ohms law is linear, the accuracy of the reading
will be determined by the accuracy of $R_2$ and $R_{3}$. It is reasonable to
take the mean square error of these accuracy figures.