The first one ordered worked 1 time, probably 30 minutes while I was familiarizing myself with the unit. Then he froze. The second seemed DOA. But. I've tried a few things and it turns out that the mount I'm using isn't conductive. I placed a piece of scrap aluminum between the milling machine table and the workpiece. And voila! It works out. So review correction: 1 star to 4 stars, no refund. Still -1 star because I can't be the first to encounter this issue and I'm wondering if there have been other bugs/DOA due to this kind of issue. In both cases, the supplied batteries have been replaced with new batteries. In both cases, the small lead that contacts the device case was torn off the LE capsule to improve contact with the device case. None of the fixes helped. The 2nd device was returned for a refund.