K8000 and PT100


I have searched the forum and found many topics about the pt100 but none of them really helps me with connecting a pt100 to the k8000.

The pt100 is an temprature resistor and I have already some installed into my circuit. The circuit looks like this:

(k8000 - 5v)------|------[pt100]-------|----[100 Ohm]------(k8000 - GND)
                  |                    |
                  |---[k8000 - AD1]----|

On the k8000 board the AD1 is fitted with the resistor as in the manual:
RA: Jumper
RB: 100K
CA: / nothing

Now when I look at the table for the pt100, at -20C the ptc is 50Ohm, at 0C the ptc is 100 Ohm, and at 90C the ptc is at 152Ohm.

The input of the k8000 board reads some changes when the temp. changes but it is not that accurate. How do I solve this ?

Thanks is advance.