Product review (1 stars): This thing sucks.
Negative stars possible? It came with some substance crusted up on the sensor area and when I tried to use it it worked at first then went to all zeros. Now it doesnt read anything but 0000. Tried to recalibrate using the included buffer powder(s). No avail. Unfortunately I didn't open it up and try it out right when I got it. So now its too late to return. Buyer beware. If you want to chance it, open it up and try it out as soon as you get it. Good luck. Maybe I can find a use for the batteries.