Scroll to the very bottom of this thread and there is a list of similar posts, The answers you seek are there.
If you live anywhere there is Sun forget the Chrony brand (sorry Erich) I tried 2 of them and all your mods. Never worked.
The Competition Electronics has never missed a shot
ProChrono Digital - Competition Electronics
For the OP:
Read the reviews. If you kill it they will replaced it for half price but if you can not shoot through a chronograph at 10 feet then maybe they are not for you.
Competition Electronics ProChrono Digital Chronograph