From b531bd45d774a07712d5ba75cc22ac7d1c8f8efc Mon Sep 17 00:00:00 2001
From: "Sam Calisch (admin)" <calisch@mit.edu>
Date: Wed, 4 Oct 2017 13:35:01 -0400
Subject: [PATCH] Update README.md

---
 README.md | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index acb98db..68ca1f1 100644
--- a/README.md
+++ b/README.md
@@ -84,4 +84,14 @@ To test this, I wrote a very simple (and slow for now!) 2D B field finite differ
 <img src='as5013-test/sim/run_single_magnet.png' width=350px>
 <img src='as5013-test/sim/run_double_magnet.png' width=350px>
 
-The pair of opposing magnets produces a high field gradient.  We could create such a region of high field gradient over each of the four outer hall effect sensors using a simple arrangement of square magnets (todo: make a drawing).
+The pair of opposing magnets produces a high field gradient.  We could create such a region of high field gradient over each of the four outer hall effect sensors using a simple arrangement of a central magnet with a surrounding annulus of opposite polarity.  I EDM'ed a test arrangment out of a large neodymium magnet of 1/8" thickness.  This went reasonably well, except for a small tab near the lead-in which was left due to the brittleness of the magnet material.
+
+<img src='magnet-arrangements/magnet-assembly-cuts.jpg' width=350px>
+<img src='magnet-arrangements/magnet-assembly-3.jpg' width=350px>
+
+I put this magnet arrangement on my stage to test the resolution.  I just grabbed the 8 bit X and Y values computed by the AS5013 and looked for the spatial range this mapped over.  Below are some very preliminary plots of this data, having not changed many of the parameters for the calculations.
+
+<img src='as5013-test/xy-plots-vs-height.png' width=500px>
+
+
+
-- 
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