I disconnected the wiper from the analog input pin and took the readings between that and ground. The voltage on the rails is 4.61 that's from the USB connection. Here are the values I got; I've only got one meter:
CW
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0 - 0.00
1 - 0.06
2 - 0.54
3 - 1.11
4 - 1.71
5 - 2.35
6 - 2.96
7 - 3.56
8 - 4.11
9 - 4.55
10 - 4.61
CCW
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10 - 4.61
9 - 4.55
8 - 4.10
7 - 3.54
6 - 2.94
5 - 2.33
4 - 1.70
3 - 1.10
2 - 0.52
1 - 0.06
0 - 0.00
Pretty much the same in both directions.
I need to get some alligator clip probes! I'm beginning to grow a third arm!