KC868-A16S Analog input 4-20mA convert not linear

[nicolouts]

Hello,

I have a KC868-A16S and I follow the exemple to read analog input from 4-20mA input.
But do you know why my raw value isn't linear?
I use analog input 4 for my test who is an 0-20mA input.
I have measure raw value from 1mA to 20mA but these value aren't linear.

What can I do?

1 mA -> 17
2 mA -> 208
3 mA -> 390
4 mA -> 582
5 mA -> 763
6 mA -> 958
7 mA -> 1140
8 mA -> 1340
9 mA -> 1525
10 mA -> 1715
11 mA -> 1906
12 mA -> 2095
13 mA -> 2287
14 mA -> 2465
15 mA -> 2663
16 mA -> 2850
17 mA -> 3045
18 mA -> 3253
19 mA -> 3483
20 mA -> 3760

thank you

Nicolouts