BeanAnimal
Premium Member
Just think 40 more 1 sentence quips aimed at the conversation, not meant to be part of it, and you may get into the selling forum... Unless of course a mod notices and starts you back at zero posts.
Stray voltage?
- Thread starter MHG
- Start date
D0GFISH
New member
I've got a good background in electrical circuits and I can see there is still quite a bit of misunderstanding here. If you use a voltmeter to measure an open circuit under a light you will see a stray voltage. The water in your tank will 'float' to some voltage but that doesn't mean current is flowing in the water which is what you worry about. A ground probe protects you at the expense of the fish because it enables a path for current to flow (through the water and fish to ground) and you may never know.
A simple, effective and cheap solution would be to buy a ~100k ohm resistor for $0.30. Stick one end in the tank and attach the other to a ground (not GFI). Make sure you don't have a ground probe in the tank and remeasure the voltage of the tank water. For example, I read ~50V when the tank is floating. When I place the 100k resistor between the tank and ground the tank voltage drops to 6V. 6V across 100k is 0.06mA current (this is very small). If I still read 50V then I have a problem. I don't know how much current would cause concern and I'd imagine it is critter dependent. BTW, you can't leave the resistor in the water long term, just test and remove. One last thing, the reason you don't want to just measure the current from the tank to ground directly is if there is a problem you are creating a short which could immediately cause injury to the fish.
Someone could put a simple circuit together to turn on an LED when current is flowing so we could identify a problem instead of masking it.
Good luck
A simple, effective and cheap solution would be to buy a ~100k ohm resistor for $0.30. Stick one end in the tank and attach the other to a ground (not GFI). Make sure you don't have a ground probe in the tank and remeasure the voltage of the tank water. For example, I read ~50V when the tank is floating. When I place the 100k resistor between the tank and ground the tank voltage drops to 6V. 6V across 100k is 0.06mA current (this is very small). If I still read 50V then I have a problem. I don't know how much current would cause concern and I'd imagine it is critter dependent. BTW, you can't leave the resistor in the water long term, just test and remove. One last thing, the reason you don't want to just measure the current from the tank to ground directly is if there is a problem you are creating a short which could immediately cause injury to the fish.
Someone could put a simple circuit together to turn on an LED when current is flowing so we could identify a problem instead of masking it.
Good luck
Well thank god for my ground probe..... Today i sold some frags to three people...had my hand in the tank twice. On the third customer I felt a tingle... like a tongue to a 9v battery... Tested again and yup a tingle. In trouble shooting I removed the ground plug. Without the ground plug, full blown electric shock..
Narrowed it down To one power strip. Moved it from my ups (both power strip were plugged into a ups) and placed it in the gfi with the ground plug. 60 seconds later the gfi tripped.... However no shock....Unplugged it all then one at a time back in, I think it's the skimmer. It's the oldest item....can't seem to duplicate it without the skimmer but the skimmer itself shows no problems in a bucket of water so I am at a loss...
Narrowed it down To one power strip. Moved it from my ups (both power strip were plugged into a ups) and placed it in the gfi with the ground plug. 60 seconds later the gfi tripped.... However no shock....Unplugged it all then one at a time back in, I think it's the skimmer. It's the oldest item....can't seem to duplicate it without the skimmer but the skimmer itself shows no problems in a bucket of water so I am at a loss...
Multimeters have a very high impedance and will not cause a short when testing between ground and tank water. If that were the case then adding a ground probe to the tank would be a bigger short then using a meter. The probe is providing a path to ground. Water has enough resistance to reduce the amount of voltage flow in the tank and therefore limits the amount of current. Thats why you are only getting 50 volts and not a full 115 volts. Adding the resistor increases the resistance even more therfore reducing the voltage to only 6 volts. Sticking the meter probe into the ground of a GFCI outlet will have the same affect as any other outlet that is bounded to the same grounding system. Adding a resistor to a tank is not reducing the amount of voltage in the tank just the measurable amount that you can measure. That voltage leak is still there.
D0GFISH
New member
koijoy - your information is not accurate. A multimeter measuring voltage has high impedance but when measuring current the impedance is very low as I stated. Its called an Ammeter and must be low impedance. And pure water has high resistance but salt water is low resistance. Voltage doesn't leak in the same sense as current - voltage can float with negligible current flow.
animalkingdom
New member
i just stand on the lid of a salt bucket when i stick my hand in the basement tank. then I dont get shocked 
