I don’t know if I am the only one who’s ever considered doing this (and quit laughing), but really it work like a champ. The IAC5 has a impedance of 169k ohms which at first I thought would too high and might not work. Connecting 120 vac to terminal 1 on the module and then terminal 2 to a tank probe which is immersed produces right at 660 micoAmps current flow which is probably not enough to give you a shock (maybe a tickle). Just make sure that the probe common is connected to neutral and whala…in a snap-iac5 you have 4 tank probe sensors for $45. It seems to work perfect. In fact I also measured a probe that was not immersed and the current was 140 micoAmps. I have to assume this is capacitive leakage on the wiring circuit. One might argue that there is a possibility of the input juction failing shorted and to that I would say you could install a 125mA fuse in line to terminal 1 on the IAC5 and that would blow probably in less than a millisecond is the junction fails shorted.