Hi Bennet,
The current sensor is connected to A0 of the arduino.
The assumption is a 4-20ma hydraulic pressure sensor which measures to about 250BAR.
Using a 250Ohm resistor to convert that current to a 1-5v signal.
But it is converting 1-5v input to 0-250 BAR pressure value. And the switch off threshold can be set in AgOpenGPS, so anything that suits your needs can be attached to A0 as long as it makes a bit of sense 
Does that answer your question?