I bought some 22-2 flexible shielded cable, 4 feet for $1.50, to reconnect the sensor to the meter. This, because the coiled cable that it comes with is too short for dunking the sensor 2 feet down in the tank. The cable didn't need to be shielded, but that was the closest I could come to the 24-2 cable on the unit. I soldered and taped the connections, with the new cable going through a tight fitting hole in the acrylic housing. To act as a strain relief I just knotted the cable right inside the housing. Without that the cable could be jerked loose from the diode. And, good news, it still works!
Now to decide on how to waterproof this. Suggestions???