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Thread: Optical sensor current leak

  1. #1
    Regular Vistor
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    Optical sensor current leak

    Tried a search.

    Im a new user. I’ve set up my ATK and all seems to work great. However I noticed some electrical leak I can feel when I touch the water. A tingling sting when I touch the water. I can make this stop by unplugging the optical sensors so I can only assume there is some electrical leak. It’s mild but noticable. I did have everything else unplugged and narrowed it down to my heater and these sensors. Heater leak is much worse but these give a current as well. I’ve hooked up my multimeter but not sure what current to look for. DC?

    Thoughts? Sensors seem to be working fine.

  2. #2
    Frequent Contributor zombie's Avatar
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    Optical sensors only use 5V, which the human body can't feel even when wet. The sensation you felt was probably a coincidence from the heater turning off at the same time. Replace your heater.

    Sent from my SM-G965U using Tapatalk

  3. #3
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    Well, my heater is pulled out so not in the tank. I could plug it in and out and the current correlates perfectly. I do have a slight nick in my skin so maybe more sensitive.
    Maybe it’s not enough to worry about. I’ll add a grounding probe and carry on.
    Do you know if it’s 5V DC ?

  4. #4
    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by Jeff Hood View Post
    Well, my heater is pulled out so not in the tank. I could plug it in and out and the current correlates perfectly. I do have a slight nick in my skin so maybe more sensitive.
    Maybe it’s not enough to worry about. I’ll add a grounding probe and carry on.
    Do you know if it’s 5V DC ?
    The FMM outputs 5V for the optical sensor. I measured it when I hacked a custom cable harness to use the OS-1 sensors on a DOS.

    Sent from my SM-G965U using Tapatalk

  5. #5
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    Thanks.

  6. #6
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    Quote Originally Posted by Jeff Hood View Post
    I’ll add a grounding probe and carry on.
    You might give some consideration to adding a GFCI as well. Far better detection than sticking finger in tank.

    Stan

  7. #7
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    Quote Originally Posted by Jeff Hood View Post
    I’ve hooked up my multimeter but not sure what current to look for. DC?

    Thoughts? Sensors seem to be working fine.
    Set it to AC and have one probe in the ground of the wall outlet and the other probe in the water.

  8. #8
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    Ok, after testing with my multi meter it was all my heater. Was leaking 25 volts but luckily very low amps hence the little sting. Can’t explain why I felt a mild current and it went away when I unplugged the sensors. I can not reproduce it now and with my heater removed everything reads zero on my multi meter.
    I also installed a GFCI for future failures.

    Thanks again for for any feedback. All is well for now.

  9. #9
    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by Jeff Hood View Post
    Ok, after testing with my multi meter it was all my heater. Was leaking 25 volts but luckily very low amps hence the little sting. Can’t explain why I felt a mild current and it went away when I unplugged the sensors. I can not reproduce it now and with my heater removed everything reads zero on my multi meter.
    I also installed a GFCI for future failures.

    Thanks again for for any feedback. All is well for now.
    Probably just a mental thing with the optical. I have experienced a sensation when sticking my hand in a tank with 0V stray voltage after shocking the crap out of myself a bunch of times when a heater failed. Some sort of pavlovian response to the expectation the sensation could be there.

    As an aside because I am an electrical nerd, the sensation you feel is based only on voltage and the electrical resistance of your body. This creates a circuit that generates a small current through your body that your nerves can feel. The whole "high voltage doesnt kill you but high current does" that gets tossed around a lot doesn't take into account that voltage actually drives the entire thing.

    Sent from my SM-G965U using Tapatalk

  10. #10
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    Yeah, won’t lie. I was a little freaked out as I’ve been shocked pretty bad in the distant past by a power bar that got salt on it. Yikes.

  11. #11
    Frequent Visitor rkpetersen's Avatar
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    Quote Originally Posted by zombie View Post
    Optical sensors only use 5V, which the human body can't feel even when wet. The sensation you felt was probably a coincidence from the heater turning off at the same time. Replace your heater.

    Sent from my SM-G965U using Tapatalk
    Would failure of a DC return pump or reactor pump typically be something you could feel, assuming no grounding probe or GFCI? In the past, pre-GFCI, I've only gotten shocked by AC devices.

  12. #12
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    Quote Originally Posted by rkpetersen View Post
    Would failure of a DC return pump or reactor pump typically be something you could feel, assuming no grounding probe or GFCI? In the past, pre-GFCI, I've only gotten shocked by AC devices.
    Anything above 10V is within the threshold for sensation since the typical human body resistance is about 10,000 ohms and 1mA is the threshold of sensation. However, many DC devices are ungrounded on the DC side, so a failure will not cause a voltage with respect to ground that your body could feel.

    Sent from my SM-G965U using Tapatalk

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