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Grounding Probe
Pszemol wrote: Yes, it would, using your body grounded to the floor as a conductor. How is a GFCI working in your bathroom without "grounding probe"? :-) How is a GFCI on your hair-dryer working without a probe? :-) Actually, the GCFI (I believe that is the correct order of initials) is grounded when it is wired into the wall. And I believe I read that 10mA trips it. Marc -- Personal Page: http://www.sparklingfloorservice.com/oanda/index.html Business Page: http://www.sparklingfloorservice.com Marine Hobbyist: http://www.melevsreef.com |
Grounding Probe
Marc Levenson wrote in message ...
Yes, it would, using your body grounded to the floor as a conductor. How is a GFCI working in your bathroom without "grounding probe"? :-) How is a GFCI on your hair-dryer working without a probe? :-) Actually, the GCFI (I believe that is the correct order of initials) both gfci and gcfi are pointing to the same gfi or electronics device that seperates the supply from the devices when a ground fault is found. ANSI calls it a GFCI so if one were to argue there one of the ones setting the standards so they are correct :| ive seen both used though, so is a mandarin goby correct really it is because its the 'common name' not meaining much when it comes to its scientific name which neither has mandarin or goby in it. same aplies here is grounded when it is wired into the wall. your missing a step but thats ok the devices ground means little (not nothing) it really has little to do with "ground" as a third wire, in easy terms it compars what is going to a device from what is coming back, if there different it trips in electronics if there is a difference then some current is going to ground and its called a ground fault, it wont trip if there is a short, because the current going out the supply and coming back on the return will be the same, even if its too much current it doesnt know the difference. And I believe I read that 10mA trips it. you can buy these in more and less sensitive models depending on there use. Marc -- Personal Page: http://www.sparklingfloorservice.com/oanda/index.html Business Page: http://www.sparklingfloorservice.com Marine Hobbyist: http://www.melevsreef.com -- richard reynolds |
Grounding Probe ( something to read guys)
"Boomer" wrote in message ...
No Marc and after more than 10 years even the electrical wizards (which I am not) are still arguing. I don't think anyone has a real answer as it really hasn't been tested as far as I'm concerned, I just hear statements and no data. Fact of the matter is, that even with GFIC's there is still "Induced Voltage" in the water in aquariums and I don't mean "stray voltage" witch is another issue. Any electrical device in or even near an aquarium will induce voltage into the water, it has been measured 100's of times. Power cords, cables, heaters, etc., all generate an electrical field in water, which can be measured. An Amp Clamp is an electrical device electricians use to measure amps, you don't connect anything to it, the wire in question is just placed in the "C' like ring and the number of amp's is directly proportional to the induced field the cord generates. You also don't need to plug in a fluorescent light bulb in either, if you are close enough to a high tension power line, the generated fields by themselves will light the bulb. Right. But there is no way to shield every electric device or wires in the walls to get rid of this electric noise in our modern society... You would have to get rid of TV-sets, computers, electric pumps&motors, lights definetely and you will still not recreate conditions similar to what is in the ocean, couple of miles from the shore, couple hundred meters deep :-) Also, we have to remember about the dualism of the electric energy becoming magnetic energy and vice versa... Every single change in an electric field will cause a change in magnetic field so the water as a conductor, grounded or not, will never be quiet in electro-magnetic terms as long as there is a source of electromagnetic noise near by. There is no ways to recreate ocean in 100% and grounding probe does not really help here much. BTW - Amp Clamp is working simply as transformer or Hal sensor. In the first case it just measure current flowing in the wire, not induced voltage... All public aquariums with shark tanks have the water grounded, with a probe, to eliminate any stray or induced voltage, as Elasmobranches have what is called a Lorenzini Organ, which can detect, in seawater, 0.005 uV or 5nV / cm @ 0.33 meters. I just wonder what kind of current has to flow in the seawater to generate such voltage difference... You will never find a piece of the ocean that generates say 18 V induced, but a power head may/will. If it is not in the ocean it should not be in a tank. I am not questioning the stray voltage issue, just the induced voltage issue, they are not the same. All of which means, IMHO, that a GFIC w/ probe or a GFIC / without a probe doesn't solve the two problems. Maybe someone can invent, just for us, a GFIC which also eliminates any Induced Voltage, without the potential side effect of a GFIC with a probe The voltage is always measured between two points. So when you are talking about powerhead induced voltage, lets say 18V, are refering to what two points? To the ground? Or two points in different places inside tank? In the first case - fish does not care about voltages relative to the ground unless it does have contact with this ground. Similarly like birds on 20kV wire. Pszemol It is rather odd that you disagree with Gerry Parker but agree with Robert Michelson, when Michelson states "A reference on the web for empirical data on aquarium voltage and current is" http://www.aquarium.net/1298/1298_3.shtml , which is Gerry's article. Garry did not make mistake in using scope and collecting data from it. He has measured different things correctly... He made a big mistake interpreting collected data - thats all :-) When you wear a wool sweter there are thousands volts generated and you can often feel a spark. Should I be affraid touching wool sweter in the same way I should be affraid touching 20kV coming out from the electric plant? :-) It looks to me the science behind voltages, amperes, ohms is kind of fuzzy for Garry and his "educated folks". But it is only my observation. You do not have to agree with me, of course :-) I think Gerry pretty much know his P & Q 's and knows how and what he is measuring I do not know Garry, so I cannot tell you who is he, but obviously he must be also scared like hell when he is elevated at the Observation Deck in any tower like Hancock, Sears in Chicago. I am affraid to jump, but I am fine with standing there :-)) |
Grounding Probe
"Boomer" wrote in message ...
http://www-training.llnl.gov/trainin...GFCIworks.html http://www.howstuffworks.com/question117.htm Good idea of posting such info - it will help folks not familiar very much with electricity understand this discussion better... Also, I can verify I was understanding correctly how it works, so people jumping so quickly to correct me, or call a troll, have a chance now to correct themselves :-) |
Grounding Probe ( something to read guys)
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Grounding Probe ( something to read guys)
Thank you boomer for finally setting people on the right road.
Some here say a GFCI doesn't need a ground. I'm like thats how it works it needs the ground. ohh well have fun arguing with people here. "Boomer" wrote in message ... Pszemol Just for you, this should make you happy :-) "Ok. I finally did it. I finally figured out the whole mystery of stray voltages in a tank. I'll explain it, but first a disclaimer: All tanks should have a ground probe and a GFI socket. Parts of this document talk about doing unorthodox things to outlets and ground probes-- which fall under the category of "Kids, don't do this at home". Other parts talk imply that ground probes are not all that good, while is arguably true for your fish, it is not true for YOU. Don't risk death. Use a ground probe and GFI socket. Your tank is not worth your life. We now return to our regularly scheduled program... It happens all the time. Someone takes a multimeter and measures the voltage between their water and earth ground. They get 30 to 60 volts and then panic, thinking that this is somehow bad and that they should do something to get rid of it. They then post a question on the net and they get dozens of answers saying the same thing, "The stray voltage is caused by electrical induction with your pumps. Use a ground probe to get rid of it". Sometimes, this stray voltage is fingered as the cause to fish stress, Head and Lateral Line Erosion (HLLE), and other mysterious fish deaths. I'll cut to the chase here and say that both of these are incorrect. Induction is not the cause of stray voltages. Ground probes are not going to remove it. And it cannot possibly be the cause of fish deaths. I can't imagine how these myths got started, especially since it is very easy for someone to find the true cause of stray voltages. The true source of the stray voltages is capacitive coupling, not inductive coupling and not resistive. Ground probes (or a multimeter) actually complete the circuit for electricity to flow. Since electricity doesn't flow unless the circuit is completed, electricity won't be flowing in a tank without a ground probe. Therefore, mysterious fish deaths in tanks without a ground probe cannot be attributed to stray voltages since current is not flowing in the tank to begin with. I'm about to go into a long, technical explanation for the cause of stray voltages. If you don't want to read it, you can stop here. I've said/typed all the important practical information already. I realize that what I'm saying goes against decades of common misbelief so some proof is required. What follows is the proof. For the proof, I assume that you know basic electricity. Ohms law, resistor dividers, and the general properties of transformers, capacitors, and inductors. You don't need a great deal of this knowledge, but enough so that you can picture what's going on since there are no pictures in this post. To find the source of this stray voltage, we must eliminate sources that don't fit the evidence. Possible sources are induction, resistive coupling, and capacitive coupling. There are other possible sources, but the odds of these being the cause are so remote that we can ignore them. Here is the evidence that can be easily measured: o The "stray voltage" changes (and is repeatable) depending on what is turned on-- including the lights. o If you put a resistor between the ground probe and earth ground, and measure the current through the resistor, you will measure up to about 40 uA. The voltage across the resistor will depend on the value of the resistor, according to ohms law. o The stray voltage/current does not change with the position of the ground probe. o The voltage measured between two ground probes is zero, regardless of their position or orientation. o If you disconnect the NEUTRAL line to the pumps/lights/etc. while leaving HOT connected, the stray voltage almost DOUBLES! o The resistance, as measured by my multimeter, between the ground probe and neutral/hot of the pumps/lights/etc. is infinite (I.E., open). Let's start with induction, since that is the common myth. If this were happening, then electrically the tank would look like a transformer. The wiring in the pumps/heaters/lights would work like the primary coil of the transformer. The water itself would be the secondary coil. Unfortunately, the evidence does not support the induction theory. In a transformer, if current is not flowing in the primary then no current will flow in the secondary. If induction were the cause then disconnecting HOT would cause the stray voltage to go to zero, not double. If induction were the cause, then almost zero current would flow through the ground probe but we have 40 uA. If induction were the cause, then moving the ground probe around the tank, or using two ground probes, would give us different results. Conclusion: It's not induction! So that leaves resistive coupling, or capacitive coupling. Electrically, resistive coupling would look like a voltage divider. One resistor of the divider would be the insulation (or lack there of) surrounding the pumps. The other resistor would be the multimeter itself, the ground probe, or a real resistor that we put in. You can actually calculate the "resistance" of the insulation using ohms law. Let's assume that we have 25 uA of current flowing. Using ohms law then X ohms = 120 volts / 0.000025 Amps, or 4.8 Meg ohms. My multimeter is calibrated for up to 40.0 ohms, so it should be able to measure this without problems. But since it measured as an open circuit, they resistance theory can't be correct. Two notes about resistance... You'll notice that I didn't take into account the resistance of the water or the resistor that I used to make the current measurements. That's because those things have much less resistance than the estimated 4.8 meg ohms. It was a shortcut for sure, but the resistance of the water and resistor was less than 100 kohms, or about 2% of the total resistance. Also... The way most people measure the stray voltage is by placing the multimeter between the tank and earth ground. In this case, the multimeter itself acts as one resistor in the voltage divider. The multimeter has a high, but finite, resistance. That's why I used a separate resistor between the ground probe and earth ground, and measured the voltage across this resistor. The resistor was anywhere from 100 to 100k ohms. When you have a two resistors in parallel, one of low value and the other of high value, the low value resistor will be dominant. The high value resistor (the multimeter) will not play a huge electrical role and mess up the measured values. In this way, I could be assured that my measurements were correct. With capacitive coupling, you must know that a capacitor can behave like a resistor when an AC current is applied to it. The resistance is proportional to, and increases with, frequency. The formula for calculating the resistance at a given frequency is: Resistance = 1 / (2 * Pi * Freq * Cap), where resistance is in ohms, freq is in Hz, and Cap is in Farads. So, with capacitive coupling is set up exactly like the resistive coupling above but with a cap as the electrical link between the AC Mains and the water. If we expect to see a 4.8 meg ohm resistor, then we can use the above formula to find the expected capacitance. So... 4.8 meg Ohms = 1 / (2 * Pi * 60 * Cap). Solving for Cap gives us 552 pF. My multimeter will measure capacitance, but it isn't calibrated into the 1000 pF range. So I expected some "not quite right numbers". I measured the capacitance between the ground probe and hot or neutral at around 1100 pF. This was suprising, since I didn't expect the numbers to be that far off. That's when I did the "disconnect neutral and leave hot connected" experiment. In this experiment the stray voltage doubled! Then the numbers made sense. At 1100 pF, 60 Hz, and 25 uA, the resistance of the cap should be about 2.4 meg ohms. This should cause double the current to flow through our voltage divider, which causes our measured voltages to be double. The evidence matches this perfectly when neutral is disconnected. With neutral connected, the AVERAGE VOLTAGE inside the pumps, lights, etc. is exactly half of the 120 volts applied to it. That's because of the voltage drop from the current flowing through it. When we disconnect neutral, there is no current flowing so there is no voltage drop. When there is no current running through the pumps, then the average voltage is 120 volts. This explains why the voltage doubles/halves depending on the neutral connection. So, now all the evidence points to capacitive coupling! For capacitive coupling to work, a circuit must be formed. This is normally done by a ground probe (or the multimeter). If there is no circuit, then there cannot possibly be any current flowing! People claim that once they add the ground probe then they cannot measure any more stray voltage-- thus the ground probe must have removed it! This is, of course, not true. Essentially, what's happening is they are measuring the voltage drop across a zero ohm resistor (the ground probe). And of course there will be no voltage drop across such a resistor! That's why they claim that it went away. Naturally, life is more complex than that. It's not a zero ohm resistor, since you have to take into account the resistance of the water and the proximity of everything. But generally speaking, adding the ground probe will bring the measured "stray voltage" very close to zero. Conclusions: 1. Very Important! Use a ground probe and GFI for your safety. 2. "Stray Voltage" is caused by capacitive coupling, not induction. 3. There is nothing you can do about it, unless you don't use electricity in your tanks (including lights). 4. A ground probe will cause, not prevent, current from flowing in a tank. 5. The lack of current flowing has never been attributed to the death of anything (except the lack of the normal electrical impulses in the brain and nervous system). So, ground probes cannot possibly solve things like HLLE, fish stress, etc. I hope that this removes a lot of the popular myths that have been circulating for decades about stray voltages in our tanks! David Kessner "I've been employed as an electrical engineer for almost the last 20 years, and everything that David wrote is completely legit. The only claim that I can't back up is the one concerning whether electrical fields and/or currents can cause diseases in fish, but that's only becuase I don't know much about the physiology of fish.." Hans Lehmann So the issue is still unsolved on whether fish are affected or not I'm surew you will enjou all of this in this thread http://groups.google.com/groups?hl=e...1eecc.16483120 %40NEWS.erols. com&rnum=6&prev=/groups%3Fq%3Dskates%2Bgroup:rec.aquaria.marine.ree fs%26hl%3 Den%26lr%3D%26 ie%3DUTF-8%26selm%3D3601eecc.16483120%2540NEWS.erols.com%26 rnum%3D6 |
Grounding Probe ( something to read guys)
Boomer quoted Someone who wrote:
o The resistance, as measured by my multimeter, between the ground probe and neutral/hot of the pumps/lights/etc. is infinite (I.E., open). This is odd. In North America the resistance between ground and neutral should be zero as neutral is connected to ground at the power panel. The resistance between hot and ground or neutral should be infinite. Let's start with induction, since that is the common myth. The author claims there is no inductive coupling, but we know there must be. When there is a moving magnetic field (from powerheads and other pumps) there will be current flow. It may be correct to say that the inductive coupling is minimal. The other paper supports this theory. If induction were the cause, then moving the ground probe around the tank, or using two ground probes, would give us different results. This I have serious problems with. I would like to see the theory that supports the argument. |
Grounding Probe ( something to read guys)
humm stiring up the mind
SG wrote in message ... Boomer quoted Someone who wrote: o The resistance, as measured by my multimeter, between the ground probe and neutral/hot of the pumps/lights/etc. is infinite (I.E., open). This is odd. In North America the resistance between ground and neutral should be zero as neutral is connected to ground at the power panel. The resistance between hot and ground or neutral should be infinite. yea odd, is there a different way of isolating the neutral/ground/hot wires elseware i know us US ppl can be odd sometimes. Let's start with induction, since that is the common myth. The author claims there is no inductive coupling, but we know there must be. When there is a moving magnetic field (from powerheads and other pumps) there will be current flow. It may be correct to say that the inductive coupling is minimal. The other paper supports this theory. an issue for me is, even with minimal remember my issue is i had a ****ed off ray :) what you might say is minimal might be ****ing this ray off. capiable of picking up voltages well below the meters, the scope does pick up things they wont, but even then the ray might pick up even more, the people shock factor for me is seriously minimal no arms go in this tank when anything is pluged in anyways and i dont have kids to stick there hands in it. If induction were the cause, then moving the ground probe around the tank, or using two ground probes, would give us different results. This I have serious problems with. I would like to see the theory that supports the argument. I never thought that 2 ground probes would give a different result I have 2 1 in tank 1 in sump interesting worthy of closer examination i didnt place the 2nd for any reason only because i figured better safe than sorry also the scope did show different values based on where in the tank the probe was positioned maybee the meters used in his "test" were not capiable of the difference. -- richard reynolds |
Grounding Probe
Boomer wrote in message ...
LOL " mandarin goby" , yup I know what you mean Richard, but that fish has often been put in the wrong family by hobbyists, who 'think' it is Goby but actually is a Dragonet and not a Goby and whats up with that how stoned was the person that made the link between Callionymidae and dragonet and "ray fined fishes" -- Boomer :) just some minor humor mixed in with minor facts :) -- richard reynolds |
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