The ON button will bind and drain the battery, if you are careful you can avoid this by fiddling with it to make it loosen . Amprobe Light Meter (non-LED) I have the same design but the button doesn't stick. So it could just be a party problem. Everything worked fine until the start, the meter readings differ by about 5% between LED and non-LED meters. Otherwise this review would have deserved 4 or 5 stars. Update: It hasn't been a problem every time I've finished using this gauge to check that the button isn't stuck, so I'd rate this one 4 stars now.