when pressing the on button of my salter electronic aquatronic 3009 scale four zeros come up on the screen, then turning into one zero, and without using the scale,the zero goes away and Err comes up, and the scale does not work at all.on the back of the scale it says:Err means overload!, but there is nothing on the scale. i also put a new set of batteries in to the scale, but the problem is the same like with the old batteries. please help thank you!!