146 lines
6.5 KiB
TeX
146 lines
6.5 KiB
TeX
%! TEX root = ../thesis.tex
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\chapter{Results}
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In this chapter all results from the experiments, as well as reasons will be discussed.
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\section{Calibration\label{calib}}
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This calibration process yielded some workflows for use inside the system as well as calibration values for the used PowerIt.
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\subsection{Calibration-Database}
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The obtained calibration values for the in these experiments used PowerIt, are combined in \autoref{pitdb}.
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\begin{listing}[H]
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\centering
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\minty[%
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minted options={lastline=10}%
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]{yaml}{pitstop/pitdb.yaml}
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\codecaption{
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PITDB entry for B05 PowerIt.
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\mintinline{cpp}{id} is obtained by the firmware and unique to each STM32Chip.
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The \mintinline{cpp}{name} corresponds to the label on each PowerIt.
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All \mintinline{cpp}{poly*} are all polynomial coefficients in order of 0th degree to 2nd degree.
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}%
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\label{pitdb}
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\end{listing}
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And to compare, the values in \autoref{lst:pitdb-example} are theoretical values, obtained from all equations in \autoref{ch:theory}.
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\begin{listing}[H]
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\begin{mintyfig}[]{yaml}
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---
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uuid: 'default'
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name: 'Bxx'
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poly18i: [-3.0, 25.0, 0.0]
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poly48i: [0.0, 227.27, 0.0]
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poly10v: [0.0, 4.0, 0.0]
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poly18v: [0.0, 1.0, 0.0]
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poly48v: [0.0, 27.386, 0.0]
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\end{mintyfig}
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\codecaption{%
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Default PITDB entry for any PowerIt.
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All \mintinline{cpp}{poly*} are all polynomial coefficients in order of 0th degree to 2nd degree.
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}%
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\label{lst:pitdb-example}
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\end{listing}
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\subsection{Accuracy}
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To obtain an accuracy for the internal measurements, the experimental sweeps can be repeated after calibration.
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One example of a calibrated measurement can be seen in \autoref{fig:postcalib10v}.
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\begin{figure}[H]
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\centering
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\vspace{-1.5cm}
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\hspace*{-.15\columnwidth}
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\includegraphics[width=1.3\columnwidth]{../pitstop/20180825/postcalib_10v.pdf}
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\vspace{-1cm}
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\caption{%
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Voltages after calibration.
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Sweep from \SIrange{43.2}{52.8}{\volt} input voltage resulting in a range from \SIrange{8.64}{10.56}{\volt}.
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The errors in the bottom diagram show the differences between reference and PIT values.
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}%
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\label{fig:postcalib10v}
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\end{figure}
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This repeats the calibration measurement for \SI{9.6}{\volt}.
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Here quite similar values can be observed, with a maximum \(\Delta V\) of around \SI{31.676}{\milli\volt}.
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It is also possible to see a systematic error in \autoref{fig:postcalib10v}.
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This error could be corrected, but requires quite some time investment.
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It would allow for a reduction of \(\Delta V\), up to a value of \SI{24.456}{\milli\volt}.
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This result is similar to others, and for all it would be possible to achieve a bit better fits.
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\section{Regulation}
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\subsection{Resulting Observation}
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To verify the regulation is working and to see if the prediction in \autoref{fig:regswrm} is correct new values were measured.
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These Values are the voltages with regulation enabled at different Reticles (see \autoref{fig:postreg}).
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\begin{figure}[H]
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\centering
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\vspace{-1cm}
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\hspace*{-.15\columnwidth}
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\includegraphics[width=1.3\columnwidth]{../pitstop/20180825/ret_vdip.pdf}
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\vspace{-1cm}
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\caption{%
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Observed AnaB voltages after regulation at multiple reticles.
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Reticle \#40 shows the best-case scenario with the least amount of V\(_\text{drop}\).
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Reticle \#5 is a worst-case scenario, with the highest V\(_\text{drop}\) while still being a usable reticle.
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}%
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\label{fig:postreg}
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\end{figure}
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In this figure three different reticles (\#5, \#29 and \#40) were measured.
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Observable is, that firstly the regulation, which was set to achieve \SI{1.8}{\volt} is working until I\(_{ana}\) is at about \SI{80}{\ampere}.
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There the minmal potentiometer setting is used.
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From here further regulation, with the same hardware, is impossible.
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Secondly the voltages for different reticles is different and not equal.
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This was one of the assumptions in the SWRM.
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To describe that behavior a distance based model (\autoref{sec:dwrm}: DWRM) could be the solution.
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And third, under the assumption of a constant fit (up to I\(_{ana} \approx \SI{80}{\ampere}\)) a systematic error can be observed.
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\begin{figure}[H]
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\centering
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\includegraphics[width=\columnwidth]{../pitstop/20180821/reticle_variance.pdf}
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\caption{%
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}%
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\label{fig:reg}
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\end{figure}
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\subsection{Distance Wafer Resistance Model (DWRM)}\label{sec:dwrm}
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Although the through SWRM gained functions approximate the real world, it is not exact enough.
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In a wafer, the distance between reticles and voltage connector (see \autoref{fig:mainpcb}) are resulting in additional resistance.
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Therefore the DWRM could be adapted.
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Circuit~\ref{fig:retmodelshell} visualizes a model, in which each different distance from the voltage connector, is classified with an additional resistance.
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\begin{figure}[H]
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\centering
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\includegraphics[width=.5\columnwidth]{tikz/reticlepower_2}
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\caption{Modified model of the to measure resistances and their currents.
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Similar to SWRM \(R_0\) describes the resistance of a connection between the PowerIt Output, up to the FET (depicted as switch), while \(R_1\) is a Resistance between FET and Reticles. But additionally \(R_{0+}\) described a Resistance, that depends on the distance between reticle and voltage connector.
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The measurement is done between output terminals on the PowerIt and pins on a Analog readout board}%
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\label{fig:retmodelshell}
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\end{figure}
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With this model the voltage is now expected to change depending on the reticles distance instead of being the same. The distances inside a wafer are visualized in \autoref{fig:retmodelrdist}
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\begin{figure}[H]
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\centering
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\hspace*{-.14\columnwidth}
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\includegraphics[width=1.2\columnwidth]{../pitstop/20180821/reticel_rtheo.pdf}
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\vspace{-1cm}
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\caption{Distances of reticles to the nearest voltage supplying connection for DWRM, distance is in reticle-side length}%
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\label{fig:retmodelrdist}
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\end{figure}
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Additionally this model is a better fit to the already observed voltage distribution in \autoref{fig:wrdist}. |