I have a simple water alarm sensor that runs off of 9V battery. It is very similar to this product.
So basically the way Alarm sensor works is, it has 2 wires extending from it where one of the wires always carries about 9V. When the wire carrying 9V comes into contact with the other one, the alarm goes off. I was wondering if there is a way to detect this with Arduino. I tried connecting the 9V battery - to my arduino GND and then lowering the voltage to 3.3 volts and feeding it to an analog pin on Arduino, but it does not work.