Hi Scott,
There's an oversized 5/16" hole off to the left to go onto the positive battery terminal and the left-most vertical cut electrically isolates the circuit.
Here's a picture I posted of the first probe. I cobbled the little sensor onto it and then potted it and coated it with plastic dip... which is the reason I had to build a second probe for debugging!
It works (now) and is well protected so I'll use it and keep the second as a backup.
Thanks again,
- Ed.
