how much stray voltage is ok?

[choirboy]

I have spent a couple hours surfing the net (one of those was just spent here on RC) and tried to find out

"How much stray voltage in a reef tank is too much"

I find all sorts of references both here on RC and all over the net, but nothing definite, and no numbers. I know there must be many differences of opinions about it but what is ok. Is. .003 ok? or is .064 ok?. Or how about 2.4?, or 15.3?. Or even 34, or maybe 78, or even in the hundreds? What number is "no prob" and what number is "starting to be bad"?

Does anyone know?

 

[hollister]

Any stray voltage not good. These means somethings not water tight or properly grounded or insulated and could just get worse. You could use a volt meter and unplug each device to find culperate and replace.

 

[oscarinw]

+1 with hollister. None is acceptable. It could lead to a number of bad outcomes.

 

[choirboy]

I guess I was trying to get some hard numbers for others who have the same question.

I bought a pretty nice digital volt meter today, got readings of 6, later got 2.8, went to lfs and bought a grounding probe, now tank reads .003.

Just wondering what hard numbers are ok, what hard numbers mean you are pushing things, and what levels are just plain dangerous to your livestock.

This post hopefully is here that others can look this up and see what general consensus people suggest to follow

 

[hollister]

I think bertoni knows how to check with the meter.

 

[choirboy]

there isn't too much to using the meter. make sure you have a good battery installed (if appropriate) plug the black probe in the black hole on the meter, the red probe in the red hole on the meter, plug the other end of the black probe into one side of the plug in an extension cord (extension cord must be plugged in to the wall), and then put the red probe end into the water in the tank. The stray voltage will show in the meter window. Mine is digital but analog work just as well.

 

[TY31088]

My first thought is, Why are you asking?
Did you get shocked?

 

[Jamaharon]

This reminds me of a project that was offered during my college years. so Fish and wild life service has a contraption that stunned the fish. It was made up of two electrical probes and had a electric current running through it. What happens is the fish gets trapped in the current and gets stunned. they would then float to the water surface to get collected by the rangers.

The thing is, you have to watch the current to stun the fish and also killing the fish. The fish actually died a little after being unstunned due to spinal column damage. the electricity actually compressed the fish spinal column leading to their death.

As for your question. I dont know how much voltage is required to kill a fish but when checking the voltage, its kind of difficult. If you place

-------------------------
-----------B--B----------
-------P---------N-------
-------------------------
-A--------------------A-

If you take above example where the P and N is the positive and negative, that is going to be the greatest difference in voltage. The voltage difference at A's are going to be different then the voltage difference between B's. So if the fish is swimming near the A's it would probably be fine, but if it swim between P and N then its not going to be good.

You should instead check for current since that is the killer.

How I would check it is positive node in water (doesnt matter the location) and negative to ground. (dont take my words on it since its been a while that I touched EE stuff)

Let me know if this works or if someone else is better at EE then me, listen to them instead. mine skill is very rusty

 

[choirboy]

to TY31088

I checked the voltage because everything seems to check out and my lfs said maybe that was my prob. I have had the tank up for 5 months. I check the water twice a week and it is ALWAYS consistent and in the right place. So since I have lost about 6 fish over the months and couldn't think of any other reason, and since the lfs said check the voltage, that is the reason.

he is very knowledgeable with 35 yrs experience and a very nice store. So I thought I would check.

 

[Jamaharon]

there isn't too much to using the meter. make sure you have a good battery installed (if appropriate) plug the black probe in the black hole on the meter, the red probe in the red hole on the meter, plug the other end of the black probe into one side of the plug in an extension cord (extension cord must be plugged in to the wall), and then put the red probe end into the water in the tank. The stray voltage will show in the meter window. Mine is digital but analog work just as well.

Make sure you plug it into ground, not the negative. I think that might be why you are seeing a voltage.

 

[Timfish]

you might also check a glass of aquarium water to see if part of the stray voltage is being induced by the metal probes in saltwater. Any stray voltage that disappears when equipment is unplugged I would say is a bad sign.

 

[dkeller_nc]

Remember that "stray voltage" measured in the way that you're describing has little to do with danger to your aquarium's inhabitants.

Specifically, if there's a potential between your aquarium's water and a particular grounded outlet, that doesn't necessarily mean there's current flowing through the water. Think of it this way: you scrape your sock feet over the carpet in the winter. After doing so, you might have a potential of a few thousand volts relative to ground. But you don't feel it until you touch a grounded metal appliance (or someone else!) and get a shock.

All current flowing through a conductor can induce an electric potential in a nearby conductor (in this case, your aquarium water). This is a function of magnetic field strength induced by the current flowing in the primary device - the voltage potential measured in the secondary device/conductor will vary with the square of the distance to, and the current flowing in, the primary device.

Similarly, if you have multiple circuits feeding your aquarium's devices (not just multiple outlets), you can easily be measuring the difference in potential between those different circuit's grounds. This is called a "ground loop" and doesn't necessarily mean that there's something wrong with your house electrical system, because electrical devices in your house can induce a (small) voltage on different grounding paths back to the circuit box.

If you really want to know if you actually have a problem, you need to measure the current potential, not the voltage. All electrical meters have a way to do this - you usually plug one of the probes into a different socket on the front of the meter, and place the meter in the potential current path. In this case, you can disconnect the aquarium's grounding probe from the house ground, and attach the meter between the probe and the house ground. You should see no more than a few milliamps at the most. If you're getting tenths of an amp or higher, it's time to go fishing for a broken aquarium device (usually a powerhead).

 

[jerpa]

remember that "stray voltage" measured in the way that you're describing has little to do with danger to your aquarium's inhabitants.

Specifically, if there's a potential between your aquarium's water and a particular grounded outlet, that doesn't necessarily mean there's current flowing through the water. Think of it this way: You scrape your sock feet over the carpet in the winter. After doing so, you might have a potential of a few thousand volts relative to ground. But you don't feel it until you touch a grounded metal appliance (or someone else!) and get a shock.

All current flowing through a conductor can induce an electric potential in a nearby conductor (in this case, your aquarium water). This is a function of magnetic field strength induced by the current flowing in the primary device - the voltage potential measured in the secondary device/conductor will vary with the square of the distance to, and the current flowing in, the primary device.

Similarly, if you have multiple circuits feeding your aquarium's devices (not just multiple outlets), you can easily be measuring the difference in potential between those different circuit's grounds. This is called a "ground loop" and doesn't necessarily mean that there's something wrong with your house electrical system, because electrical devices in your house can induce a (small) voltage on different grounding paths back to the circuit box.

If you really want to know if you actually have a problem, you need to measure the current potential, not the voltage. All electrical meters have a way to do this - you usually plug one of the probes into a different socket on the front of the meter, and place the meter in the potential current path. In this case, you can disconnect the aquarium's grounding probe from the house ground, and attach the meter between the probe and the house ground. You should see no more than a few milliamps at the most. If you're getting tenths of an amp or higher, it's time to go fishing for a broken aquarium device (usually a powerhead).

+1