That implies you do have a mains ground. GFCI = Ground Fault Current Interrupter.

An American electrical engineer taught me how to wire up the US Siemens GFCI breakers, they are connected to the 2 hot wires and an autotransformer to power up the circuit. It's not connected to ground. However, if any hot line in my whole house touches anything like wet concrete from rain, it shuts down immediately due to the sense current. So Ground Fault Current Interrupter means it interrupts when hot line leaks to ground or earth as it produces unbalance return current in the sense coil.

 

re mains wiring, yep seen some truly amazing things on my trips around world,
but a common is
electricity companies do not provide a earth, they transmit the electricity 3 phase , normaly delta, 3 live wires only. no neutral or earth,
https://www.electricaltechnology.org/2014/09/delta-connection-power-voltage-current.html

at the local sub station, that three phase is split , normaly by transformer, into three single phase lines, each with a neutral,
neutral is normaly, but not universal, straped hard to a big spike in the earth at the sub station,,

these two wires then go to your house,
normaly, at the house, the neutral is bonded to a separate earth around the house.
yes in theory, the neutral and earth wire in the house are the same voltage!

but as I said, I've seen some real scary systems,
not least was a shower in the usa, using plastic pipes , to the metal shower heater / shower head, in a kids summer camp , where there was so much leakage that if you were tall and touched the shower head you got a nice tingle..

 

your missing the point

its current flow that is the problem your trying to sort both in esd and your pick-up problem you started with.

thought experiment.,

make your pan 6 by 6 meters,
every thing you have is inside that pan,
everything is connected electrical to that pan,
no mains coming in, all battery powered .
make pan totaly insulated from the room, no wet wire needed.

what voltage will. there be between any two points ?
what current would flow ?

I guess it's like the transmission lines with birds sitting on it, current doesn't flow into the body because there is no potential difference, although current still movse by inertia inside the wires.

But when you walk in carpet, so many statics build up in your body. So you connect to earth to dissipate them, then you can be at same potential with your circuit (provided you don't continue walking on wet carpet).

Anyway. If the neighbors fault current is running beneath my house, I guess the fault current won't affect me if I can make the house same potential because I'd be like bird sitting on the power lines.

I didn't know this 8 years ago when I installed the full house GFCIs. now I may connect all appliances metal case to the steel water pipe so if hot connects to the appliance, I'd not get shock even if I'm standing on concrete.. because it has same potential. I guess this is what others are saying me in another thread. This is additional protection in case the GFCI fails.

 

I guess it's like the transmission lines with birds sitting on it, current doesn't flow into the body because there is no potential difference, although current still movse by inertia inside the wires.

But when you walk in carpet, so many statics build up in your body. So you connect to earth to dissipate them, then you can be at same potential with your circuit (provided you don't continue walking on wet carpet).

Anyway. If the neighbors fault current is running beneath my house, I guess the fault current won't affect me if I can make the house same potential because I'd be like bird sitting on the power lines.

I didn't know this 8 years ago when I installed the full house GFCIs. now I may connect all appliances metal case to the steel water pipe so if hot connects to the appliance, I'd not get shock even if I'm standing on concrete.. because it has same potential. I guess this is what others are saying me in another thread. This is additional protection in case the GFCI fails.

walking on the carpet will yes make a voltage ,
but thats an external power being bought onto the metal plate.
no need to dissipate it to earth, if your floating metal plate is connected to you, and all the equipment is connected to the metal plate, whats the voltage difference between you and the plate ? whats the voltage between the plate and the equipment ?
no where is any of that connected to the water , what current flows in this case do you think ?

BTW. where did you come up with idea that current flows by inertia ?

 

walking on the carpet will yes make a voltage ,
but thats an external power being bought onto the metal plate.
no need to dissipate it to earth, if your floating metal plate is connected to you, and all the equipment is connected to the metal plate, whats the voltage difference between you and the plate ? whats the voltage between the plate and the equipment ?
no where is any of that connected to the water , what current flows in this case do you think ?

BTW. where did you come up with idea that current flows by inertia ?

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

 

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

so did you note the reference in that link to wire with zero resistance? the wires to you house have a very real resistance and current in them does not have momentum,

at zero degrees k or near, very weird things happen, helium liquid can run up a test tube and quantum mechanics kick in as dominant

and your answer to the questions are?

 

Ah. In EEG and ECG, amplifier reference pickup is called ground (or virtual ground). If you don't connect it, there is no signal because the inputs are floating. The word "reference" in EEG and ECG is reserved for the In- input, the In+ is called active.

Anyway. I noticed if you put the ground (amplifier reference pickup) in EEG in the wrist instead of in the head, the powerbank noise magnitude is larger. I didn't use the AC adaptor much because I avoid using it to avoid surges. Why is it if the (reference pickup) or ground is further away, the noise is larger? Is it because the resistance is more in the skin? But then, a amplifier reference invariant to the skin resistance because it just sets the common mode range of the differential input amplifer. As someone wrote in the net:

"The "ground" electrode simply tries to keep the measured bag of conductive saltwater at midpoint common mode range of the differential input amplifier.
There is ideally no current through the "ground" electrode terminals so it will bias the measured biomass blob even if it had megaohms of impedance."

(Response to post #
Moving the reference farther away is "increasing the antenna effective aperture", which will certainly pick up more of the ambient noise field, similar to how a larger antenna tends to pick up more signal.

 

(Response to post #
Moving the reference farther away is "increasing the antenna effective aperture", which will certainly pick up more of the ambient noise field, similar to how a larger antenna tends to pick up more signal.

did you mean by "reference" the electrode ground? Because in biopotential measurement device, the reference is the input In-, not the ground.

 

so did you note the reference in that link to wire with zero resistance? the wires to you house have a very real resistance and current in them does not have momentum,

at zero degrees k or near, very weird things happen, helium liquid can run up a test tube and quantum mechanics kick in as dominant

and your answer to the questions are?

It's a very common question why current seems to flow in wire without potential. Here is one good answer I read in quora:


"This is an interesting question because it shows us the limits of the model used:

If we imply an ideal wire we get zero potential between the contacts of the voltage source. This is in contradiction with the voltage source and means that we have to improve the model to better match the reality. There are two aspects, the voltage source and the wire:

The wire has, in fact, a small resistance.

If the voltage source is powerful enough, it will force so much current through the wire that the potential becomes non-zero, i.e. the voltage the source is programmed to.

If the voltage source is weak, we need to model it as a perfect voltage source with an internal resistance in series. The current is then determined by ohms law and the internal resistance (plus the very small resistance of the wire) I=U/(Internal + wire resistance)"



I'll read about it more. Sometimes I have to simultaneously read physics stack exchange electronics forums, quora, eevblogs, , mike holt, electrician forums and others. I also ask questions there from time to time.

 

It's a very common question why current seems to flow in wire without potential. Here is one good answer I read in quora:


"This is an interesting question because it shows us the limits of the model used:

If we imply an ideal wire we get zero potential between the contacts of the voltage source. This is in contradiction with the voltage source and means that we have to improve the model to better match the reality. There are two aspects, the voltage source and the wire:

The wire has, in fact, a small resistance.

If the voltage source is powerful enough, it will force so much current through the wire that the potential becomes non-zero, i.e. the voltage the source is programmed to.

If the voltage source is weak, we need to model it as a perfect voltage source with an internal resistance in series. The current is then determined by ohms law and the internal resistance (plus the very small resistance of the wire) I=U/(Internal + wire resistance)"



I'll read about it more. Sometimes I have to simultaneously read physics stack exchange electronics forums, quora, eevblogs, , mike holt, electrician forums and others. I also ask questions there from time to time.

I know a few people who read to much , and understand to little.

The web is full of little snips of information and theories .

Not all are true at all times. .

But that has little if anything to do with your interferance question

Is your or original question now answered ? .

Btw.
When. Do you sleep ? You say philapines , which is 7 hours ahead of where I am now , yet when earlier I was traveling , you seem to be on at every hour. Well impressed . I'm knackered from traveling and being up that long.

btw2. this is a great trusted site if you want to learn about emc / emi
https://www.learnemc.com/emc-resources

 

I know a few people who read to much , and understand to little.

The web is full of little snips of information and theories .

Not all are true at all times. .

But that has little if anything to do with your interferance question

Is your or original question now answered ? .

Btw.
When. Do you sleep ? You say philapines , which is 7 hours ahead of where I am now , yet when earlier I was traveling , you seem to be on at every hour. Well impressed . I'm knackered from traveling and being up that long.

btw2. this is a great trusted site if you want to learn about emc / emi
https://www.learnemc.com/emc-resources

I sleep 11pm to 6am. My last question is whether human size faraday cage can make up for lack of Driven Right Leg in bioamplifier. and vice versa... whether presence of DRL can replace Faraday cage or the latter still the best.

 

I sleep 11pm to 6am. My last question is whether human size faraday cage can make up for lack of Driven Right Leg in bioamplifier. and vice versa... whether presence of DRL can replace Faraday cage or the latter still the best.

I was considering a room sized farady cage, (actually, a shield), but that is a "big deal" to achieve. Certainly it could be an effective choice.

 

I sleep 11pm to 6am. My last question is whether human size faraday cage can make up for lack of Driven Right Leg in bioamplifier. and vice versa... whether presence of DRL can replace Faraday cage or the latter still the best.

Oh to be young and live on so little sleep.

You've not answered the previous questions weve asked , but your asking another.
That's not fair

Re Faraday cage .
Yes that could cut out external empty interference ,
But is there external interference ?

Try wrapping the person in tin / aluminium foil ! Cook at gas mark 4 ..

Remember to clamp the Faraday cage to your water tank.

Or just connect the rxb back to the person, and all will be well.

 

Oh to be young and live on so little sleep.

You've not answered the previous questions weve asked , but your asking another.
That's not fair

Re Faraday cage .
Yes that could cut out external empty interference ,
But is there external interference ?

Try wrapping the person in tin / aluminium foil ! Cook at gas mark 4 ..

Remember to clamp the Faraday cage to your water tank.

Or just connect the rxb back to the person, and all will be well.

You asked about equal potential. I answered in #149 by quoting in quora that in current flowing through wire, there is a bit resistance that is why current can flow. I'm familiar with superconductivity as I have read several books about it before when I got interested for a while in high temperature superconductors.

If you are referring to the static. If your body full of static. It is difficult to be at potential with the circuit because you need to share the static to the circuit first to equalize the potential (which can damage it), this is why first thing to do is dump the static in the body to the earth. unless your entire room and floor is made of same potential as circuit which doesn't use carpet.

After you mentioned about equalizing potential to avoid static. I pondered why birds could stand on power lines and not electrocuted. They say the current in the wire flow within the wire and not into the birds bodies because the wire has no potential difference. And people in the other thread kept telling me to connect appliance enclosure to have same potential as floor. So I wonder if they have same potential, am I like the bird that won't feel shock even if the live short on the metal enclosure and the metal enclosure is shorted to the floor and I'm touching the appliance enclosure and bare feet on the floor. This is just backup in case my state of the art Siemens GFCi breakers fail.

Btw.. as a doctor of medicine, what is your specialty before? surgeon? endocrinologist? etc. And how did you end up designing bioamplifier chip which is not the path of doctor of medicine? I'm asking in case I need your service in the future in mass producing specialty chips.

 

There are a few misconceptions in your knowledge base.

There is no inertia in the wire.

Birds are not electrocuted while standing on high voltage wires for a different reason, not because there is zero voltage.
There is current flowing in the wire and hence there must be a voltage difference in order for current to flow in the wire.

In the analog world, there is no such thing as zero current, zero voltage, or zero resistance. There is always a finite resistance in any conductor even if someone labels it as having zero ohms.

When a bird stands with both claws clutching the wire, there is a finite resistance across the wire and finite voltage across the bird's legs. The bird has resistance and hence there is finite current travelling through the body of the bird. Even though it is very small, it is not zero current. The current is not large enough to harm the bird.

The bird survives standing on a high voltage cable because the current flowing from one leg to the other is very small.

 

There are a few misconceptions in your knowledge base.

There is no inertia in the wire.

Birds are not electrocuted while standing on high voltage wires for a different reason, not because there is zero voltage.
There is current flowing in the wire and hence there must be a voltage difference in order for current to flow in the wire.

In the analog world, there is no such thing as zero current, zero voltage, or zero resistance. There is always a finite resistance in any conductor even if someone labels it as having zero ohms.

When a bird stands with both claws clutching the wire, there is a finite resistance across the wire and finite voltage across the bird's legs. The bird has resistance and hence there is finite current travelling through the body of the bird. Even though it is very small, it is not zero current. The current is not large enough to harm the bird.

The bird survives standing on a high voltage cable because the current flowing from one leg to the other is very small.

So when there is short in the hot line to refrigerator body and it is earthed. Same situation as the bird where there is more resistant in the body than in the conductor? We only see illustration like the following where circuit breaker trips in milliseconds..but let's say the breaker is faulty and won't trip, and there is continuous current in the refrigerator to earth to neutral in the top case when earthing is used. The person touching the refrigerator won't get shock even when standing bare feet? Of course this is just for sake of illustration and I won't try it of course.

 

Equipotential bodies

ESD damage is avoided by bringing two objects to the same potential, i.e. equipotential.

 

To avoid electrocuting someone connected to bioelectrical equipment, use batteries or an isolation transformer.

 

Equipotential bodies

ESD damage is avoided by bringing two objects to the potential, i.e. equipotential.

I have wooden floor in my room and when I played with the EEG at night. I wear slippers. So how do I get into equi potential with the EEG unit? The moment I touched it, i am in equipotential but that is after the static flow into it damaging the circuit.

 

Wear the anti-static wrist strap and connect it to a known grounding point.
If you don't have a grounding point, create your own by driving a piece of copper pipe into the ground.
For electrical compliance, the pipe has to be driven at least 8 feet into the ground. Do not use this as an electrical utility ground as it does not meet electrical compliance. A proper ground must be an electrical wire connecting back to the utility supply ground.