7i84 Analog inputs

I am looking to do spindle, feed and rapid override via potentiometers. I have a 7i84 that I can use. It says the inputs 0-3 can be used for analog inputs. I am looking for a little guidance on how that would be wired as well as how the HAL should work. Has anyone done this before? I was unable to find anything helpful in my searching on the forum.

Figured out the HAL required to get the analog inputs to show. I just needed to change the "sserial_port_0=0xxxxxxx" config option in the hm2_eth line to "sserial_port_0=1xxxxxxx".

I am now having an issue with the voltage not being linear even though I am using 50k linear pots. I assume this is because of my lack of electronics knowledge and some basic thing that I don't know. See the attached graph. I am using a 36v supply with the positive connected to the first pin of the pot, negative to the third pin and the input on the 7i84 connected to the wiper. I understand the dead zone on either end of the graph but I don't understand why it isn't pretty close to a straight line. I divided the ~300 degree rotation into 16 points. Here are the actual values:

1 - 0
2 - 0
3 - 1.850588
4 - 3.131765
5 - 4.128235
6 - 5.124706
7 - 5.978823
8 - 7.117647
9 - 8.683529
10 - 10.10706
11 - 11.95765
12 - 15.23176
13 - 19.50235
14 - 27.33176
15 - 36.01529
16 - 36.01529

Everything seems good enough until around points 10 or 11. Then the voltage shoots up significantly. Center on these pots reads about 7.9v.

I would appreciate guidance from anyone who knows what's going on here.

The pots I have are these:
2 - PDB181-K220K-503B (50k linear pot with center detent)
1 - PDB181-K415K-503B (50k linear pot)

I have attached the datasheet.

This behaviour is expected because the input impedance of the 7I84
is about 11 K ohms. A 50K ohm pot has an equivalent source
impedance of close to 0 ohms at either end, but 12.5K ohm source
impedance in the middle of its range. This means at 1/2 way up
the 50K Ohm pot looks like a 18V source with 12.5K of series resistance.
The means the reading in in middle of the range will be less than
1/2 the expected linear reading.

I would probably use 24V and a 5K pot.