What the .......
zombie;297509 said:
That method of doing the test is actually testing what is known as ground potential rise by referencing the voltage of the tank to the ground in your house. To test for "stray current", you need to check for a voltage difference between two points in the tank (ie. black side in one part of the tank, red side on the other). This tells you if there is a potential difference that would allow a current to flow through a fish. Continuous exposure to 0.5mA of current, which corresponds to a voltage difference of of about 0.05mV across the length of a fish (based on V=IR and average resistance of a saltwater fish at 0.1 ohm) can cause damage over a long period of time. The ground potential rise test can be useful in determining if the insulation inside the windings of a pump are starting to degrade if only one pump causes a large increase in voltage and can be an indicator that it is time to change the pump before it short circuits in the tank. If said pump with a degraded insulation were turned on and off a lot, the rapid change in ground potential rise can cause a transient change in the voltage gradient of the tank, which will allow a small amount of current to flow through fish for a very short time (1 or 2 milliseconds). The ground potential rise test can also indicate that you have a poor connection from the ground of your outlet to earth ground if a voltage is measured when no outlets are on or several outlets contribute a small change.
zombie;297495 said:
If all of your outlets are plugged into a GFCI and it doesnt trip on you when a pump turns on, there is no risk of damage to any livestock. If you want to test for "stray voltage" the correct way, you need to connect a ground rod to one area of the tank, connect your voltmeter to the same ground rod, and move the other end around the water on the mV AC setting. If it shows zero there is no voltage gradient in the tank and nothing to be worried about.
As stated above, current does the real damage, and current can only be induced if there is a difference in voltage from one end of the fish to another. A perfect example of this is how my companies lineman work on 345,000 volt lines while they are live. They fly up to it in a helicopter and the lineman connects a copper cable between himself and the 345,000 volt line which brings him to the same potential as the line. Since he is at the same potential as the line, he can touch it with his bare hands and doesnt even feel a tingle. It works the same way for stray voltage. I would venture to guess 99% of people that blamed this disease on "stray voltage" did the test incorrectly and it was not the underlying problem.
What the......
A perfect example of this is how my companies lineman work on 345,000 volt lines while they are live. They fly up to it in a helicopter and the lineman connects a copper cable between himself and the 345,000 volt line which brings him to the same potential as the line. -A linemen hooking a cable to himself and the line is no different than just touching the line - as long as no circuit is formed then there is no danger. A bird can sit on one wire just fine, just can't have the wing tips touch two different lines. No circuit, no power flow. If electricity was so predictable and safe, then more journey lineman would have thumbs left, instead of their big toe on their hand.
As stated above, current does the real damage.....-Current does damage, but so does voltage - just in a different way. Both can harm/kill you. Think pacemaker or AED. Ever mess around with a battery and a transformer in middle school? Hell of a rude shock - all voltage, no real current issue at play. Imagine getting shocked 24 / 7!!!
If all of your outlets are plugged into a GFCI and it doesn't trip on you when a pump turns on, there is no risk of damage to any livestock.- Having a GFCI outlet is for your protection, not the protection of your livestock. If power comes in from the "hot" wire, and out from the "neutral", then a GFCI will not trip. It doesn't know whether the water/fish/motor/heater is completing the circuit.
GROUND
FAULT
CIRCUIT
INTERRUPT. It means if there is no "fault" to ground, then no interruption. (Remember back in the day when electronics builders didn't have an isolation transformer in there? Oh, simpler times.)
The ground potential rise test can also indicate that you have a poor connection from the ground of your outlet to earth ground.... - Please remember that in most homes the Neutral bar and the Ground bar are joined in the main breaker box.
........you need to connect a ground rod to one area of the tank, connect your voltmeter to the same ground rod, and move the other end around the water on the mV AC setting... -Hooking one lead of the meter to the ground probe is no different than just putting that lead in the water.
Sorry for the rant. Always remember that electricity is just trying to find the "easiest" way home - ALWAYS. The path of least resistance is the easiest way - whether it be through you, water, a fish, ground rod, etc. Path of least resistance = low resistance in Ohms. Most human bodies have a resistance of 1.5 Meg ohms to 1.8 Meg ohms- the idea that prompted a grounding rod - since it has less resistance than you do. Have your house wiring inspected by a certified electrician if you are concerned. If your house is older ( 30+ years), then your home insurance company may want it inspected/replaced anyway. If you want to be 100 percent certain that no leakage exists, I would recommend that you find someone that has access to the high end / expensive electronics scopes (that will have their own power supply, to avoid ground feedback loops/voltage spikes) to actually measure individual component electricity use/seepage. May try a local electronics college and see if someone wants a side job.
May want to just try some V
eggie Rounds from Petsmart.
Late,
GC