Snap-IAC5 Module as Tank Probe Sensor

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.


Yeah, have to admit, that’s a pretty cool off the wall use. Have not heard of that one…however…
I feel strongly compelled to write some sort of disclaimer… messing with 120vAC like that is…well, not to be taken lightly.
Depending on whats in the the tank could change the leakage currents a fair bit I would suspect.
In a nut shell, ‘don’t try this at home’ and if you do and you get a kick or worse, don’t say we didn’t tell you not to do it.

Stay safe and keep sending in these off the wall, outa-the-box uses of Opto.
I just love seeing stuff like this.


Btw, this thing has been working perfect for over 4 years.

Well, I agree it’s not real sanitary, however, keep in mind that even if the input was shorted, the max current flow would be 1 ma in the event of a direct short to common. Now that would probably give you a good tickle but I’m not even considering the resistance of the human body even wet. To be even safer, I would suggest that the builder (as is actually code) to use a GFCI on the power supply to the whole control panel, and this will ensure that the system is safe.

Yes the medium would definitely come into play. If your were sensing oil, for instance, I’m not sure it would work. The problem is, if you sense something that is high impedance like oil, then you would have to lower the resistance value which would then be a safety hazard.