Problem with ACS712

I have an ACS712 current sensor break out I bought on ebay and I think it has an issue with its vout function. I put a somewhat discharged 9v battery in series with current sensing hook ups and measured the current with a multimeter at .67A. Here is where the problem is. The datasheet says the chip will output a 66mv/A voltage difference. I measured a 16mv difference with .67A flowing through it. It should be dropping 44mv at .67A right? (.67A x66mv = 44mv) I have absolutely no experience with these chips so I don’t really know If I’m doing something wrong or if it is actually working correctly. I know for a fact it is hooked up correctly. It is receiving 4.9v from the Arduino and with no current it is outputting 1.94v. Shouldn’t it be outputting 2.45v? Ill just get another one if its faulty. They’re cheap. Steve from Pa

I tested a 30A ACS712, 2.507V on output. Feeding it 4.98V from Arduino Uno board.

Thank you elac that's what I thought it should be considering it is an analog sensor. Interesting. Guess I got a bad one. Hopefully the next one I get actually works.

Swri9217: I put a somewhat discharged 9v battery in series with current sensing hook ups and measured the current with a multimeter at .67A.

Am I reading this correctly? Did you connect a 9V battery directly to the ACS712 current sensing inputs? Or did you use a resistor in series with the battery? Directly connecting a battery to the module without a load is a bad idea.

At first I used a resistor then I hooked the 9v battery alone to it. There is no way a 9v battery could provide enough current to fry the chip. I measured .67 amp from the battery in a direct short through my multimeter. I know it's a bad idea but I didn't get a measurable voltage difference on the output when using the resistor. It was misbehaving before I put any current to it anyway.