Another positive vote for the Competition Electronics Pro with the Bluetooth DigitalLink. So as others have mentioned, it's real picky about sunlight hitting the sensors. My fix was to cut a piece of cardboard and using some small spring loaded clamps to attach it to the upright wires or the plastic things they attach to. Works great! The blue tooth adapter is way too cool and makes it a snap to document a dozen rounds, then upload it to my computer via a spread sheet. It's a great tool for working up your loads, and having a quick and easy reference for later viewing. It's even Mac Friendly!