Yes, I can. If you had read the data sheet you would have realized that the sensor is Bi-Lateral, that is that the sensor will sense current in either direction... to or from the source and that the sensor is radiometric, that is that it will center itself to 1/2 of the sensor power source - Not the load voltage but the current that is to be measured as the sensor is a hall effect device and therefore isolated from it's load.... The sensor will swing about 1/2 of the sensor supply voltage in response to the applied load. This is done so the sensor can sense both drain and charge to the load power source. It will go 'above' the 'center' for loads applied and 'below' the 1/2 point for sources of 'current' applied. What you need to do is either write your sketch to sense or respond to one 'direction' (polarity) of change in voltage or apply the sensor output to a level shifter, typically made from an op-amp and some other parts to get a "Ground Referenced Output". The real issue here is that I don't think from what you have written so far that you understand very much of what I have said so far. I feel that I know what it is that you need to do, however explaining it to you is difficult because you don't have the understanding of general electronics that I do and it is more work than I really want to do. Not because I am lazy... far from it I looked at the information for your sensor and had the answer immediately... the issue is that it too difficult to explain in words and goes somewhat beyond my understanding of the scope of this forum. I have the tools to draw the diagrams and simulate it for that matter. However doing so would mean several more hours of my time and I have spent far too long at these replies as it stands now. MY take of this forum is that it is a place of learning not a place to go to in order to get your work done for you. If you carefully follow what I have said so far, I think you have enough clues except one and that is you might have to 'amplify' the swing to get it to the point where the Arduino can differentiate or accurately sense your "Trouble Condition" as the Arduino can either sense a voltage in reference to it's supply voltage or to an internal 1.1V reference Both are 10 bit measurements so at the 5V reference your "granularity is 4.88 mv / step or measurable change or 1.1/1024 if you use the internal reference. Again YOU are the engineer here not me... it is YOU WHO MUST LEARN, not me. Further if I make a mistake I have to "Fix" it... and I am NOT being compensated for my time or my responsibility in becoming what is in effect "The Project Engineer". I am happy to give advice but not to engineer the whole project. I Do Hope that what I have written so far has been helpful and if you need further help then you will have to create accurate drawings of what you need and what you have done to create this project so far. IMO
Doc