Just to be clear @MisterBill2
Are you saying you think the op original question has not been addressed ?

It's already answered because connecting the ground in the AC adaptor removes the harmonics. But let us tie up some loose ends (no pun intended). Ericgibbs mentions in message #138 here about isolation transformer. And I found out I bought one at digikey 8 years ago:




It's 230V to 115V. It's used to power a 115V surge protector. The US electricial enginner who taught me to wire up the Siemens GFCI told me to buy the Isolation Transformer. My question. What would happen if I connect the EEG AC adaptor to it?




There is still missing neutral? Can the harmonics go away? Also can the isolation transformer prevent surges? One reason I don't want to use the AC adaptor now. But still I won't use them because the isolation tranformer capacitive coupling can reach entire room. I have a very sensitive EMF meter. Ericgibbs web site in message # 138 shares the following info:

 

WRONG!!!! A GFCI device senses the difference in current between the hot and neutral circuits routed thru it. PERIOD!! SENSING THAT DIFFERENCE is totally separate from any connection to actual ground! How could it be otherwise???
GFCI outlets include a ground wire connection because the code requires the outlet to have that connection.

I will give you a real life experience.

We moved into our present house when the house was 1 year old. I had a computer set up in one room plugged into one outlet. The computer printer was plugged into another outlet. Every time I plugged in the serial cable between the computer and the printer, the GFCI at the service panel would trip. As it turned out, after painstaking investigation, I found a fault, a short between NEUTRAL and GROUND behind an outlet in a different part of the house.

The computer and the printer were plugged into two different circuits. The installer had intentionally cut the GROUND connection at the GFCI because they could not figure out why it was tripping. By connecting the printer to the computer, I was completing the connection of the GFCI to GROUND. The GFCI was tripping because it detected a fault.

Here is the likely scenario. The electrical wiring was installed by a "qualified" electrician. When the main breaker was turned on, the GFCI breaker tripped. It was close to quitting time for the day. The installer cut the GROUND connection at the GFCI and all was hunky-dory.

These were presumably "qualified" electricians. Go figure.

 

It's already answered because connecting the ground in the AC adaptor removes the harmonics. But let us tie up some loose ends (no pun intended). Ericgibbs mentions in message #138 here about isolation transformer. And I found out I bought one at digikey 8 years ago:

View attachment 354168


It's 230V to 115V. It's used to power a 115V surge protector. The US electricial enginner who taught me to wire up the Siemens GFCI told me to buy the Isolation Transformer. My question. What would happen if I connect the EEG AC adaptor to it?


View attachment 354171

There is still missing neutral? Can the harmonics go away? Also can the isolation transformer prevent surges? One reason I don't want to use the AC adaptor now. But still I won't use them because the isolation tranformer capacitive coupling can reach entire room. I have a very sensitive EMF meter. Ericgibbs web site in message # 138 shares the following info:

View attachment 354170

Great your question is answered,
please mark it as closed, and open a new post if you have questions as to say how a mains breaker works, as that is totaly irrelevant to this question.

In summary,

As you have seen,
the interference is caused by power supply noise from your power supply , and incorrect equi potential bonding, proven as you say the noise goes away when you battery powered.

as a medical device there should be no connection earth and all should be at equipotential

The flavour of mains you use is not important,
be it via a breaker of some kind , floating in a ballon or what ever
but power supply has to be medical grade, and low noise

get a power supply thats low noise, like a battery and equi potential bond,

and all will be happy

 

hi Secan,
Read through this linked info.
As an example, Mains isolation transformers are often used in electrical repair shops to protect the repair technicians
E
https://www.powerinspired.com/isolation-transformer-need-know/

FYI,

According to the OP this is a medical application, there are very strict rules as to what "earth" can and cant be used and the require isolation,

The OP is asking about harmonics, and how they are picking them up on a medical device designed to pick up mV a high impedance circuit,

The OP seems to believe that current can flow without a potential difference, via "inertia" in his house wiring,

The OP seems to think that putting a wire in the water gives them an good earth,

I hope they are not using a standard off the shelf none medical isolation transformer , as they seme to want to connect them selfs to the water tank,

@Secan

be aware, isolation transformer is great, and is normal practice for say old fashioned TV repair work, when the metal work is connected to one side of the mains,
BUT: The isolation transformer has two output terminals
put our left hand on one, and all is ok, take left hand off, and put right hand on the other terminal and all is well,
now put your left hand on one terminal and your right on the other terminal,
you will get a mains level shock,
For10 points, can you explain why the above works,

 

I just read it in the following url a while ago while googling all i can about all this:

https://physics.stackexchange.com/q...n-flow-between-2-points-at-the-same-potential

Yes, and that says that in the absence of resistance then ..
your wire has resistance, so this post is not applicable

 

Stepping back a bit, considering that the noise is present when the supply is used, but not when batteries are used, two real possibilities: #1. The noise is coupled from the mains, thru the supply, and into the amplifier. OR #2, The noise is generated within the supply, and coupled int o the amplifier.
The label on the supply says it is medical grade. The bad news is that might not be true. The worse news: some people lie! and some labels are false.

 

Great your question is answered,
please mark it as closed, and open a new post if you have questions as to say how a mains breaker works, as that is totaly irrelevant to this question.

In summary,

As you have seen,
the interference is caused by power supply noise from your power supply , and incorrect equi potential bonding, proven as you say the noise goes away when you battery powered.

as a medical device there should be no connection earth and all should be at equipotential

The flavour of mains you use is not important,
be it via a breaker of some kind , floating in a ballon or what ever
but power supply has to be medical grade, and low noise

get a power supply thats low noise, like a battery and equi potential bond,

and all will be happy

Can you please give an actual product example of a medical grade power supply that is floating? you mean nothing is connected to ground like below? The following is supposed to be medical grade (see label). I want to see example of no ground medical power supply and floating:

 

FYI,

According to the OP this is a medical application, there are very strict rules as to what "earth" can and cant be used and the require isolation,

The OP is asking about harmonics, and how they are picking them up on a medical device designed to pick up mV a high impedance circuit,

The OP seems to believe that current can flow without a potential difference, via "inertia" in his house wiring,

The OP seems to think that putting a wire in the water gives them an good earth,

I hope they are not using a standard off the shelf none medical isolation transformer , as they seme to want to connect them selfs to the water tank,

@Secan

be aware, isolation transformer is great, and is normal practice for say old fashioned TV repair work, when the metal work is connected to one side of the mains,
BUT: The isolation transformer has two output terminals
put our left hand on one, and all is ok, take left hand off, and put right hand on the other terminal and all is well,
now put your left hand on one terminal and your right on the other terminal,
you will get a mains level shock,
For10 points, can you explain why the above works,

I know potential difference can drive current, like holding each end of the isolation transformation can still shock you of course. In house wiring, there is potential difference between the power line transformer that drive all the current in the house.

About inertia. I was just reading in stack exchange about a small section of wire where current flows. Note that in physics stack exchange there are hundeds of Ph.D and experts of experts. Here are some arguments:

How electric currents can flow between 2 points at the same potential? - Physics Stack Exchange

"The electric field accelerates charge. A flow of charge does not require an electric field in the absence of resistance. Think of it this way: in a resistor, the flowing charge carriers interact with the structure of the resistor, losing kinetic energy in the process. To maintain the current, the flow of electric charge, an electric field is required to accelerate the charge. In the absence of these interactions, when there is no resistance to the flow, the charge carriers loose no energy to the wire and thus, require no electric field to maintain the flow.
– Alfred Centauri CommentedNov 25, 2012 at 2:19 "

" Charges have mass. Once you start a mass moving its motion will not change if there are no forces acting on it. So you start the charges moving and as the wires are ideal and offer no impediment to the motion of the charges, the charges will carry on moving. "

The first quote above was not describing about superconductor. Only the last sentence in the following last Answer mentioned it as reference. Of course the topic is not saying all the wiring in our houses uses superconductors. Whatever. Are you saying all of their answers are wrong about inertia in small section of wire and the true answer is there. There is still small potential difference?? If so, then must add Answer to it to debunk the other claims.

"It is possible because potential gradient defines the electric field and if the gradient is absent then the electric field is also absent so there is no force that the charge career can feel and if the mobility of the career is at its maximum (which can be achieved when electrical resistance is vanishing) AND there was already a current before the started being equipotential. Through classical physics arriving at this fact, only one thing drives the formulation and that is when a body in an inertial frame is moving then it will keep on its same pace though there is no force required. Actually, the electrical version of it is achieved by imposing statistical laws on this law of inertia of classical mechanics. Even it is achieved yet in a condition which is called superconductivity. In such superconductor materials current keeps on flowing for a sufficiently long duration even after withdrawal of potential difference across the conductor."

 

Stepping back a bit, considering that the noise is present when the supply is used, but not when batteries are used, two real possibilities: #1. The noise is coupled from the mains, thru the supply, and into the amplifier. OR #2, The noise is generated within the supply, and coupled int o the amplifier.
The label on the supply says it is medical grade. The bad news is that might not be true. The worse news: some people lie! and some labels are false.

Just considering the addition of ground which removes the harmonics should have rested the case. But I googled drjohsmith floating power supply and came across the so called Body, Body Floating (BF) and Cardiac Floating (CF) levels of medical power supply. I'm looking for a circuit schematic to see how they are able to remove the ground, and whether it can eliminate the harmonics without using ground. If a BF power supply is not expensive, i'll get one to try it. But if it is so expensive. I just want a circuit schematic of how BF and CF power supplies are designed where no ground is required. I need this understanding since I have to eliminate the capacitive coupling of the harmonics in the surrounding. I still have difficulty acquiring Faraday Cage.

 

When I googled for schematics of medical power supplies. I still see ground at the source. Only the applied part doesn't have ground. If Body Floating (BF) and Cardiac Floating (CF) means only the applied part has no ground while the source still connected ground. Then all medical supply has ground at source. If this is so. then that means when you don't use the ground at source, the harmonics occur (like mine). If this is so. Then it's fully answered and thread closed by you categorically declaring all medical power supply have ground at source. If you deny this, then pls show schematic with no ground at source and how they manage to do it.

 

I'm looking for a circuit schematic to see how they are able to remove the ground, and whether it can eliminate the harmonics without using ground.

If the harmonics are clearly identifiable and are not blocking or modifying your wanted other signals, can't you simply ignore them?

 

If the harmonics are clearly identifiable and are not blocking or modifying your wanted other signals, can't you simply ignore them?

I can easily remove the harmonics by grounding the source of the AC adaptor. But I don't understand why Misterbill2 is seeking other origin of the harmonics. Unless he didn't get what I said before that grounding the AC adaptor can totally remove the harmonics (99%)?

 

Just considering the addition of ground which removes the harmonics should have rested the case. But I googled drjohsmith floating power supply and came across the so called Body, Body Floating (BF) and Cardiac Floating (CF) levels of medical power supply. I'm looking for a circuit schematic to see how they are able to remove the ground, and whether it can eliminate the harmonics without using ground. If a BF power supply is not expensive, i'll get one to try it. But if it is so expensive. I just want a circuit schematic of how BF and CF power supplies are designed where no ground is required. I need this understanding since I have to eliminate the capacitive coupling of the harmonics in the surrounding. I still have difficulty acquiring Faraday Cage.

Well done for following
It's all about this equi potential we keep mentioning.
If there is no voltage difference , current can't flow and no pickup .
Read up some more on this before you connect a human to a mains power supply.

 

I can easily remove the harmonics by grounding the source of the AC adaptor. But I don't understand why Misterbill2 is seeking other origin of the harmonics. Unless he didn't get what I said before that grounding the AC adaptor can totally remove the harmonics (99%)?

You can not randomly ground a medical power supply.

 

You can not randomly ground a medical power supply.

The one shown in post #187 has a ground symbol on it, and the mains input has a standard 3-pin mains cable socket with a ground pin. So it seems that particular medical supply is intended to use a conentional mains ground.
I note that the amplifier has a "potential equalization conductor" at the back, which presumably would be used for bringing patient, operator and amplifier common to the same potential using wrist straps? I couldn't see any instructions for its use in the user manual.

 

I can easily remove the harmonics by grounding the source of the AC adaptor. But I don't understand why Misterbill2 is seeking other origin of the harmonics. Unless he didn't get what I said before that grounding the AC adaptor can totally remove the harmonics (99%)?

is that the medical psu you have ?
you can not randomly ground a medical power supply.
that schematic , shows two filter capacitors to safety ground. you note safety ground is isolated from the patient.
but in that system, if the earth is not connected , then the chasie is now connected to the mains voltage by capacitors, these leak, and can cause a shock if the person is connected to a real earth and touches the case as the power in is with reference to earth.

thats why there are very strict rules on medical power supplies,

if your medical power supply,y needs three wire mains, live neutral and earth , then you need to connect a good earth .

do not add other earth's,

 

There were bot harmonics and noise shown. They come from different sources.

 

The one shown in post #187 has a ground symbol on it, and the mains input has a standard 3-pin mains cable socket with a ground pin. So it seems that particular medical supply is intended to use a conentional mains ground.
I note that the amplifier has a "potential equalization conductor" at the back, which presumably would be used for bringing patient, operator and amplifier common to the same potential using wrist straps? I couldn't see any instructions for its use in the user manual.

Note the potential equilization conductor at back is just a connector, it is not even connected to the unit case as the photo below shows:






Here is the use of it that Alec_t allerted me in message #69 that it must be connected.




You mean the potential equalization conductor must be connected to ground, to the same ac adaptor ground? But then the generic adaptor schematic shown in message #190 illustrates as drjohsmith emphasized that there is capacitor to main which can shock you if the ground is not competent. Does Globtek adaptor have the same capacitors to main? I can't find schematic of Globtek or Jameco medical supplies? Do they have the capacitor in mains connected to ground too?

Also does potential equalization conductor means the earth ground? If not, how do you make a potential equalization conductor in the room that doesn't use the ground, so the AC adaptor ground can't share the same conductor as the potential equalization conductor at the back of the unit (in the photo above). The gtec technical support told me one must touch the conductor at back before handling electrodes to avoid statics. He didn't tell me to connect it to room potential equalization conductor. And I'm the only user of the unit, meaning I only put the electrodes in myself. the above quote says in the first line that electrodes must not be connected to earth. so if I touch the potential equalization conductor at back, won't the electrodes be like contacting it via my skin? But then maybe my skin high resistant is what made it possible. but then if the ac adaptor main ground is connected to the back potential conductor and there is no competent earth as drjohsmith warned, then I can be shocked.

 

Note the potential equilization conductor at back is just a connector, it is not even connected to the unit case as the photo below shows:

View attachment 354235


View attachment 354236

You mean the potential equalization conductor must be connected to ground, to the same ac adaptor ground? But then the generic adaptor schematic shown in message #190 illustrates as drjohsmith emphasized that there is capacitor to main which can shock you if the ground is not competent. Does Globtek adaptor have the same capacitors to main? I can't find schematic of Globtek or Jameco medical supplies? Do they have the capacitor in mains connected to ground too?

Also does potential equalization conductor means the earth ground? If not, how do you make a potential equalization conductor in the room that doesn't use the ground, so the AC adaptor ground can't share the same conductor as the potential equalization conductor at the back of the unit (in the photo above). The gtec technical support told me one must touch the conductor at back before handling electrodes to avoid statics. He didn't tell me to connect it to room potential equalization conductor. And I'm the only user of the unit, meaning I only put the electrodes in myself. the above quote says in the first line that electrodes must not be connected to earth. so if I touch the potential equalization conductor at back, won't the electrodes be like contacting it via my skin? But then maybe my skin high resistant is what made it possible. but then if the ac adaptor main ground is connected to the back potential conductor and there is no competent earth as drjohsmith warned, then I can be shocked.

NO, the "potential equalization conductor" must connect to the patient and the equipment operator. THOSEare the sections of the system that must be at the same potential, whatever it may be. This is not guarding against mains power shocks, this is providing the same zero volts reference for all parts of the instrumentation system.

 

NO, the "potential equalization conductor" must connect to the patient and the equipment operator. THOSEare the sections of the system that must be at the same potential, whatever it may be. This is not guarding against mains power shocks, this is providing the same zero volts reference for all parts of the instrumentation system.

I just used multimeter a while ago to check the continuity of the potential equalization conductor and the unit casing, I was mistaken, they are connected. A PCB is one large copper so the connector at the back is connected to the casing and ground.

But if the same conductor is connected to me without the 10Megaohm resistor in the antistatic wrist band. Won't I get a shock if the AC adaptor capacitor ground and the room conductor got detached from the earth as drjohsmith warned. Or should 10Megaohm always be used when I connect to the room potential equalization bar. I thought drjohsmith said the ground must not be connected to the patient (I am both the operator and patient because I only used the unit on myself).

Also my room is in second floor so there must be a wire to connect it the earth at lower floor (street level). Imagine the potential equalization bar is in the street level. Maybe need to separately wire them to earth so if the AC adaptor ground got detached. Won't get electrified. But then, does Globetek, Jameco or other medical supply indeed have that capacitor to ground in the schematic in message #190 warned by drjohsmith?

What is the best medical supply that is 100% reliable model so maybe I can buy it and cut open my existing AC adaptor to see if there is a capacitor from live to ground inside.