Is stray Current Normal?
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wholelottawater
New member
may I ask how did you take your measurement?
iamwrasseman
New member
normal ? well most tanks have some but i wouldnt call it normal .
125G Reefer
New member
52 volts is a bit much. That would be considered high, while 5 is about normal.
I used a multimeter, stuck one probe in the ground inlet of an extension cord, the other probe in the tank.
If your getting more than a mere couple of volts from an individual piece of equipment such as a heater, that item is leaking as opposed to causing induced voltage. So I'd recommend replacing those items. Heaters especially are prone to having their seals leak and are probably the number one culprit in such cases, with powerheads following as a close number 2.
The measure of voltage on a floating wire (if there were no leak) will depend heavily on the meter used. To say "it should be small" isn't really accurate... It will never read 0, and what it does read depends on the size of the resistor and sensitivity of the internal circuits in your meter. You'll never be able to tell what is real voltage and what is phantom voltage. If your meter reads 120v, it's not phantom. Anything else "small" you just don't know.
When in voltage mode you don't want the meter to actually impact the circuit you're measuring. You can't just measure voltage potential, it actually measures the current that flows between the two wires. To do this, without impacting the circuit it's measuring, it uses a very, very, very, large resistor inside between the common and voltage inputs. It measures tiny currents flowing across that resistor and then calculates voltage from V=IR. You have a known current and a known resistor, so you know voltage.
What are the phantom voltages in the tank caused by water movement, electrical noise, etc? Very, very high voltage potentials, with practically no current. Well, guess what the meter is measuring? Teeny tiny currents... Depending on the size of the resistor and the sensitivity of the circuitry in the meter, there's really no telling what the meter will read. It's going to measure whatever current is there, scale it way up and try to average out a voltage.
Read current instead. That turns the meter into a wire, no large resistor, no wacky meter behavior.
There should be a sticky created on this. Every time i hear someone measuring voltage on the tank i cringe. From an electrical engineering perspective it makes no sense at all. The only thing normal consumer volt meters can accurately mesaure on our tanks is current.
When in voltage mode you don't want the meter to actually impact the circuit you're measuring. You can't just measure voltage potential, it actually measures the current that flows between the two wires. To do this, without impacting the circuit it's measuring, it uses a very, very, very, large resistor inside between the common and voltage inputs. It measures tiny currents flowing across that resistor and then calculates voltage from V=IR. You have a known current and a known resistor, so you know voltage.
What are the phantom voltages in the tank caused by water movement, electrical noise, etc? Very, very high voltage potentials, with practically no current. Well, guess what the meter is measuring? Teeny tiny currents... Depending on the size of the resistor and the sensitivity of the circuitry in the meter, there's really no telling what the meter will read. It's going to measure whatever current is there, scale it way up and try to average out a voltage.
Read current instead. That turns the meter into a wire, no large resistor, no wacky meter behavior.
There should be a sticky created on this. Every time i hear someone measuring voltage on the tank i cringe. From an electrical engineering perspective it makes no sense at all. The only thing normal consumer volt meters can accurately mesaure on our tanks is current.
wholelottawater
New member
Thanks for the info..
So your saying the multimeter is useless in my case?
From your professional perspective is it possible for you to make a thread on how to accurately perform the reading. Thanks :beer:
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So your saying the multimeter is useless in my case?
From your professional perspective is it possible for you to make a thread on how to accurately perform the reading. Thanks :beer:
<img src="http://i71.photobucket.com/albums/i154/DETANE1/SAM_1634.jpg" border="0" alt="Photobucket"></a>
You should be able to measure current with your meter. Double check your manual, but it appears that your meter uses the same input for both mA and V. To measure mA current your inputs would stay the same as they are for voltage, but the dial would be set to mA. One wire on ground, one wire in the water, just like you did when measuring voltage. Unplug equipment until you get a reading of 0 mA. You should be able to actually get to a solid 0, no guesses.
wholelottawater
New member
Are you having a problem with your tank??
By doing this test all you are going to show is that your tank has a potential or lack there of one. You will likely find a current is present just as you did find a voltage. Our tanks our full of inductive and resistive devices that can and will induce small currents or voltage potentials.
If you are having a problem with you tank there is likely another problem IMO. If you are doing this for information purposed and experimentation do not let any results panic you if nothing is going wrong with you system.
Most importantly be careful and ensure that your tank is on a proper GFCI.
By doing this test all you are going to show is that your tank has a potential or lack there of one. You will likely find a current is present just as you did find a voltage. Our tanks our full of inductive and resistive devices that can and will induce small currents or voltage potentials.
If you are having a problem with you tank there is likely another problem IMO. If you are doing this for information purposed and experimentation do not let any results panic you if nothing is going wrong with you system.
Most importantly be careful and ensure that your tank is on a proper GFCI.
With all due respect to our electrical engineers, a few decades of practical professional aquarist experience has taught me that anytime one is seeing the amount of voltage the OP reports, there is a faulty piece of equipment. While I fully agree with the problems of measuring low voltage,on the order of a couple of volts, once you start talking larger numbers such as 50, that measuring error is really just background noise for our purposes.
Yes, that's pretty much exactly what i said.
"The measure of voltage on a floating wire (if there were no leak) will depend heavily on the meter used. To say "it should be small" isn't really accurate... It will never read 0, and what it does read depends on the size of the resistor and sensitivity of the internal circuits in your meter. You'll never be able to tell what is real voltage and what is phantom voltage. If your meter reads 120v, it's not phantom. Anything else "small" you just don't know."
If you read 50, there may be a correlation, for _YOUR_ meter. You can't extrapolate that out to any meter for any person and give advice based on it. But, with all due respect, without measuring current you cannot say for certain whether or not you have thrown away perfectly good equipment because you read a voltage when it's on... It may induce a "high" voltage according to your meter, that correlates directly to it being on and off, but the equipment actually be perfectly fine. If you found damage it was clearly the cause, but without clear damage then making an assessment based on voltage could lead people to throwing away perfectly good equipment.
"The measure of voltage on a floating wire (if there were no leak) will depend heavily on the meter used. To say "it should be small" isn't really accurate... It will never read 0, and what it does read depends on the size of the resistor and sensitivity of the internal circuits in your meter. You'll never be able to tell what is real voltage and what is phantom voltage. If your meter reads 120v, it's not phantom. Anything else "small" you just don't know."
If you read 50, there may be a correlation, for _YOUR_ meter. You can't extrapolate that out to any meter for any person and give advice based on it. But, with all due respect, without measuring current you cannot say for certain whether or not you have thrown away perfectly good equipment because you read a voltage when it's on... It may induce a "high" voltage according to your meter, that correlates directly to it being on and off, but the equipment actually be perfectly fine. If you found damage it was clearly the cause, but without clear damage then making an assessment based on voltage could lead people to throwing away perfectly good equipment.
Lets put it this way. In nearly 30 years ranging from running pet shop fish rooms with the same equipment as a hobbyist uses, to aquaculture facilities using 3 phase equipment (such as heaters), (and a couple dozen different meters in that time) I've yet to see 50 volts of induced voltage. It's always come down to faulty equipment that either replacing the item or resealing the wiring entry points as resolved and reduced said voltage to that mere few volts that you refer to
It's a case of real world experience vs. theory. What gets interesting is different peoples sensitivity to the voltage. I've had staff and students reported feeling a "tingling" sensation or shock in tanks where I've felt nothing. Typically, breaking out the old voltmeter has shown levels around 30 to 60 volts. Measured this too many times with too many different meters to be willing to chalk up my safety or anyone elses to the idea that it's just meter inaccuracy. Anyone who wants to wait till they see some nice full blown electrolysis of a major failure is welcome too, but I'll never advise it
20 years of hands on electronics experience, plus a degree in computer engineering from a top 10 university graduated with honors (which is basically electrical engineering with a focus on digital circuits). I'm only 2 years in on reefkeeping, so i'm not going to be giving husbandry advice any time soon, but electronics i do know.
Multimeters just aren't designed to be used in this way, theory or practice. You might have some success using them like this, but more likely than not you're going to be throwing away perfectly good equipment and running into oddities that you can't explain. If you look around here, you'll see that repeated over and over in any of the threads about this. Tons of anecdotal evidence and conflicting findings, no real science.
I'm not a chemist, I'm not going to claim to be a chemist. I haven't heard of anything that would lead me to believe that there would be any source for current going to ground other than an insulation failure. I know enough about chemistry to know that I don't know enough to say anything about it though. 0 current certainly means your safe. >0 current implies there's a failure, but maybe there's some natural process in the tank that would produce it?
Multimeters just aren't designed to be used in this way, theory or practice. You might have some success using them like this, but more likely than not you're going to be throwing away perfectly good equipment and running into oddities that you can't explain. If you look around here, you'll see that repeated over and over in any of the threads about this. Tons of anecdotal evidence and conflicting findings, no real science.
- If there is a failure in the insulation, there will be current flowing to ground.
- voltage in the tank does not mean that there will be current flowing or failure in insulation, that voltage may be "phantom" voltage due to the nature of how the meter reads and averages it's readings.
- The size of the "phantom voltage" you read will depend heavily on the meter you use and the equipment that's causing it.
I'm not a chemist, I'm not going to claim to be a chemist. I haven't heard of anything that would lead me to believe that there would be any source for current going to ground other than an insulation failure. I know enough about chemistry to know that I don't know enough to say anything about it though. 0 current certainly means your safe. >0 current implies there's a failure, but maybe there's some natural process in the tank that would produce it?
