What is the correct ammeter wiring?

I bought an ammeter which I would like to connect in my car. This ammeter is a gauge available on Aliexpress and has only two poles (some ammeters have a third negative pole). I wired from one side the alternator (+), and the battery(+) on the other side but the pointer doesn’t move at all. When I start the engine and the lights it will move a little but then it will reset its position. Am I doing something wrong? Thanks for your help.