I was measuring voltages directly only connecting NI9207 (AI0+ and AI0-) and voltage source (+ and -), I got wrong readouts. I tested using a know voltage source and comparing multimeter value with NI-MAX task (see Ni-MAX task.JPG) for checking.
Using the configuration like wiring.JPG the problem was resolved. But I have to use a 1M resistor for each voltage channel for getting right measurements.
Is there any solution for improve this scenario? I mean avoid using 1M resitor for each voltage channel