how to use the KMI15/1T1 Rotational sensor with Arduino UNO Rev3?

I am trying to measure the RPM's of a fuel engine which has gears. I have received a free KMI15/1T1 sensor but when I reference the data sheet it only uses 2 pins: you have to supply 12V and depending on the rotation the current will change from 7 mA to 14 mA.

Any suggestion how I am going to measure this with the Arduino?

(eg: 15 modules / sec = 15 Hz Current from 7 mA to 14 mA back and forth)

On page 10 of the datasheet you see the typical application circuit. You can measure the voltage over RL which should be in the range of 0.8V to 1.7V so measurable with any analog input of the Arduino. If you need a higher resolution, you might either change the analog input reference voltage or use an amplifier (or both).