Need help with voltage dividers

Other Hardware General Electronics
3

CrossRoads:
Try this: 5V to sensor to Analog pin, 10K from analog pin to Gnd.

Sensor at 9K, Vout = 5 * 10000/(9000+10000) = 2.6V
Sensor at 30K, Vout = 5 * 10000/(30000+10000) = 1.25V

Stick in other values for 10000, if you want.
If you go bigger, need to allow more settling time for the ADC to give accurate readings.
If you go smaller, the resulting range gets smaller.

With resistances that high and a small output voltage range I'd also add a 0.1uF capacitor between analog pin and GND to help with radio noise.