We don't know what, if any, components inside the amplifier are connected or coupled to that conductor, so we can't give a definitive answer.

Its only coupled to the unit metal casing. I have opened the unit, it's not connected to the PCB or electrode ground.

 

So it can't be used for providing a useful reference voltage (virtual ground); only for equalising the potentials of patient, operator and whatever else it connects to outside the amp. The manual says to connect it to the potential equalization conductor of the room where the unit is used, but it seems you don't have one of those.

 

So it can't be used for providing a useful reference voltage (virtual ground); only for equalising the potentials of patient, operator and whatever else it connects to outside the amp. The manual says to connect it to the potential equalization conductor of the room where the unit is used, but it seems you don't have one of those.

When there are optocouplers that isolates the inputs side, there is always virtual ground that is also isolated from main unit casing. Why would anyone make isolated inputs then connect the virtual ground to the casing and into the potential equalization conductor? is there any unit who do this?

Anyway. I need to know something since MrChips didn't response to whether shunting to ground can remove capacitive coupling in body after inquiring it many times before.

I don't own oscilloscope except the pocket Fnirst TCO which was broken already. Please touch your table top oscilloscope probe - you'll see 50Hz or 60Hz signal, which is capacitively coupled through your body to mains. Now if you touch the earth, would the 50Hz or 60Hz vanish? So I can decide whether to continue wearing anti-statis wrist band and connect to earth instead of connecting to the g.USBamp potential equalization conductor which I don't see any purpose since im NOT connecting the unit to AC adaptor but only using all batteries including laptop in battery with AC adaptor not plugged in.

 

If you can open the unit, try and find out where the R and G connections go.
Take pictures of both top and bottom sides of the board.

 

I said to ignore capacitive coupling through your body.
Your body is an antenna. It will pick up all sorts for EMI.
Yes, if you touch the probe tip and the ground clip at the same time, EMI pick up will be reduced.

But you don't want to connect the wrist band to earth ground because you will be compromising patient safety.

 

I said to ignore capacitive coupling through your body.
Your body is an antenna. It will pick up all sorts for EMI.
Yes, if you touch the probe tip and the ground clip at the same time, EMI pick up will be reduced.

But you don't want to connect the wrist band to earth ground because you will be compromising patient safety.

This was what I've been asking for 1 month already and not answered in the other thread continuous fault current in the earth.

Supposed my neighbor has hot line contacting earth which didn't trip his breakers because of resistant in the soil and the fault current continuously travel under my earth to the pole transformer ground. Would the fault current go up my wrist band? But then it has 10 Megaohm resistor in series, so the current that would reach me would only be 220V/10000000= 2.2microAmpere. There is no danger here. So what is the concern? Pls elaborate as I've been asking the details for one long month and others seemed to be either not understanding it or saying its unnecessary concern.

 

This was what I've been asking for 1 month already and not answered in the other thread continuous fault current in the earth.

Supposed my neighbor has hot line contacting earth which didn't trip his breakers because of resistant in the soil and the fault current continuously travel under my earth to the pole transformer ground. Would the fault current go up my wrist band? But then it has 10 Megaohm resistor in series, so the current that would reach me would only be 220V/10000000= 2.2microAmpere. There is no danger here. So what is the concern? Pls elaborate as I've been asking the details for one long month and others seemed to be either not understanding it or saying its unnecessary concern.

let's take this new question of yours.,

your neighbour house has a fault, so its mains is connected to the ground connector, but it does not blow the circuit breakers in their house .
first question you need to decide is what current will flow.,
lets take a numberbof 20 Amps, it's a crazy number, as the wiring is going to probably burn out even if the fuse / breaker has not popped.
say this crazy current flows under your house .
what voltage will your house see ?
you have said a few times here, your area is humid, so I assume your ground is not dry,
the resistance of the wet ground is thus going to be very low, its infinitely wide conductor,
so what voltage will you see under your house, basically 0,
now, despite your comment in other thread about current flowing by momentum without a voltage, it does not,
You need a voltage difference to make a current flow.
so as their is zero voltage under your house caused by this 20 amps, there is zero current that flows up to your wrist.

 

let's take this new question of yours.,

your neighbour house has a fault, so its mains is connected to the ground connector, but it does not blow the circuit breakers in their house .
first question you need to decide is what current will flow.,
lets take a numberbof 20 Amps, it's a crazy number, as the wiring is going to probably burn out even if the fuse / breaker has not popped.
say this crazy current flows under your house .
what voltage will your house see ?
you have said a few times here, your area is humid, so I assume your ground is not dry,
the resistance of the wet ground is thus going to be very low, its infinitely wide conductor,
so what voltage will you see under your house, basically 0,
now, despite your comment in other thread about current flowing by momentum without a voltage, it does not,
You need a voltage difference to make a current flow.
so as their is zero voltage under your house caused by this 20 amps, there is zero current that flows up to your wrist.

I believe now the 2 golden rules

1. Never earth patient or EEG user by wrist band (or any conductor)
2. Always connect potential equalization conductor and never earth it.

For #1. Electronic folks always work with unplugged (not powered circuits). While for patients/users, the EEG/ECG leads are connected to the skin. And some patients are unconscious so they can't jump up and yell about being electrified. So never ground patients to avoid ground fault.

For #2. There may be potential difference between two parts of the surgery room and if the surgeon got potential difference and touched the live heart, it can get into shock. So imagine one day we are the patient being operated on, we must insist or yell "Potential equalization conductor engaged, and ground connection disengaged" to the AI machine task checker in the operating room.

That said. I have never seen a medical power supply that is not earthed at the source side. All Globtek medical supply is earthed at the input side. drjohsmith, you said you used unearthed source medical power supply. Pls mention a brand or model because I couldn't find even one after days of googling. Thanks.

 

I believe now the 2 golden rules

1. Never earth patient or EEG user by wrist band (or any conductor)
2. Always connect potential equalization conductor and never earth it.

For #1. Electronic folks always work with unplugged (not powered circuits). While for patients/users, the EEG/ECG leads are connected to the skin. And some patients are unconscious so they can't jump up and yell about being electrified. So never ground patients to avoid ground fault.

For #2. There may be potential difference between two parts of the surgery room and if the surgeon got potential difference and touched the live heart, it can get into shock. So imagine one day we are the patient being operated on, we must insist or yell "Potential equalization conductor engaged, and ground connection disengaged" to the AI machine task checker in the operating room.

That said. I have never seen a medical power supply that is not earthed at the source side. All Globtek medical supply is earthed at the input side. drjohsmith, you said you used unearthed source medical power supply. Pls mention a brand or model because I couldn't find even one after days of googling. Thanks.

your getting there @Secan

rule one , and only rule is
do no harm, dont kill the patient ..
my hope is you never have the screaming patient you mention, and our intention here is to try to guide you away from that happening,

you have been jumping all over with these different topics, and referencing different forums, worried about current that you say flows in mains wirring by momentum with put a drving voktage etc, so I can see how confusion comes about

I am worried in that in some of your posts you insist you only use battery power, no mains for this medical work, and yet here you are again asking about medical grade power supplies you want to use.

which is it ?

you are also making wrong statements, you make claim :

"1. Electronic folks always work with unplugged (not powered circuits"

this is explicitly not true, and over the posts you have been shown many examples where this is not true ,

its safest if the circuit is discharged and at equipotential with the electrician, but it is not required.

do not ground patients is also the safest . current flow across say a heart is a critical worry, and as was shown in one of your other posts, a floating patient is less likely to suffer a situation where a sustained dangerous current can flow.

but there are some experiments where a subject needs to be connected to earth ,
this is always well reviewed , and supervised by responsible professionals due to the inherent risk,

similar circuits to ecg, are also used in lab test on things like dissected muscle to see drug effects, or even single cells, which might , not being a living person or animal could be connected to earth. most machines I've seen support this by having a very obvious, I.e. can't be done by accident, method of connecting the earth.

the operating theater , and direct heart connection is an even more strictly regulated environment as such a low current can cause death .
e.g. cardio stimulator direct to heart use 10 of volts, external use hundred of volts, and much more charge .

As for mains power supply,
no medical equipment would rely upon an external brick on a rope for isolation, its just too easy for someone to plug in the wrong adapter.,

you were in multiple posts discussing harmonics and interference.
a good medical grade psu, would not output harminics on its dc side .
your supply you mention, which you seem to have opened, thus violating its ability to be used in medical work, seems to need a mains earth on its input side to avoid harminics being seen on the dc side.
my guess is your supply has feed forward capacitors across the medical isolation, and a y capacitor filter on its mains side .
none of this would make me happy with that mains adapter.
you also said your laboratory / medical test area has no earth connection, so you had a bit of wire , resting in a big bucket of water outside resting on a concrete pad.

this meets no regulation I know of.

I would be a lit happier if you sticked to the battery option you said you used .

 

I've been wondering why you asked where R and G go. So I studied about Driven Right Left, Amplifier common, virtual ground, etc. so I can understand where you are coming from:

Here is what the inside looks like


View attachment 354563

Each bank of 4 channels with separate Reference and Ground have own isolation circuit not connected to the potential equalization conductor.

1. First, have you come across an EEG or ECG that has the potential equalization conductor connected to the unit electrode ground or reference? If not. Why do you ask where the R and G connected to?

2. You know in a typical hardware based instrumentation amplifier, R or Reference is In-, Active is the In+, and the ground. But then in the g.USBamp which is similar to Biosemi (see below) which doesn't use instrumentation amplifier but uses ADCs to deduct common mode by software. I think the Reference also uses ADC. Before I thought there was a instrumental amplifier inside for Channel 1 to Reference for example. But today I think they are all ADCs including the R(eference). How can I tell if the Reference is ADC or instrumentation amplifier? First. I'm familiar with its use. If you connect channel, 1, 2, 3, 4 and use the Reference. It's unipolar montage where the 4 channels uses one Reference (the blue below). Can pure ADC use this technique ? In the PC software, we can't see the raw Reference ADC recording, only other channels 1. In the software, you can't use unipolar montage either. Only by hardware. The bipolar montage is only able to deduct say channel 1 to channel 2 by software.

View attachment 354565


There are separate banks of 4 channels where the reference and ground is separate (as you see in the manual). In the PCB above, the 4 banks have separate circuit. . They uses the ADUM2400 isolator so it uses DC to DC converter to isolate. And no, the potential equalization conductor is NOT connected to either R or G. I can't open the see the other PCBs below because they are double side, and I can't open the top one without bending some pins connected inside:


View attachment 354564

First some briefing by Biosemi that was not available or used in your thesis days:

Biosemi EEG ECG EMG BSPM NEURO amplifiers systems

"During the early nineties, researchers kept asking for systems with higher dynamic range (to allow DC measurements), better channel separation, and more channels than could practically be achieved with the Shared-ADC-setup. Advancing developments in low-power, high-bit ADCs and low-power Programmable Logic Devices (PLD) allowed designers of modern multichannel acquisition systems to switch to the ADC-per-channel setup. BioSemi already introduced the new setup on the Mark-6 system in 1995, and has since then continued to improve the setup in terms of miniaturization, power consumption and reduced costs. The ADCs operate synchronously, so no sampling skew is present (all ADCs perform the conversion at the same moment). The multiplexing operation is now performed entirely digital, so any deterioration of the signal is eliminated. The dynamic range of the system can now be really equal to the dynamic range of the ADC. The 24 bit ActiveTwo with its 110 dB dynamic range and >110 dB channel separation is a good example of the advantages which can be achieved by using one ADC-per-channel. Specs like these are fully unattainable with the older setup (30-40 dB worse, a factor of nearly 100)."

I'm sorry you were convinced to open a medical unit .
Your doing medical research on humans , a very regulated industry .
Im cerain you know, in most countries, only qualified professionals are allowed to work on medical equipment, that is used on humans.
I have feeling you are not so qualified, so this equipment is not longer medical approved and can not gpbe used on humans or sold / passed on as medical approved .
sorry, but its only useful for the bin now .,

 

I'm sorry you were convinced to open a medical unit .
Your doing medical research on humans , a very regulated industry .
Im cerain you know, in most countries, only qualified professionals are allowed to work on medical equipment, that is used on humans.
I have feeling you are not so qualified, so this equipment is not longer medical approved and can not gpbe used on humans or sold / passed on as medical approved .
sorry, but its only useful for the bin now .,

I opened it more than a year ago, took many pictures of different angles, and never opened it again because I don't want to damage any part.

It was initially approved for use in medical in the early 2010s but now it is no longer used for medical. That is why the product is now called g.USBamp Reseach in their website. Only for Research use. They said it was so expensive to pay for approval and since it is mostly used in BCI (Brain Computer Interface) project, then it is no longer approved for used in medical. In the following instruction for use in their other product. They are meant to use the potential equalization conductor to ground to earth. Maybe in transitioning from Medical to Research device, the original advisors are long gone so forgot to emphasize never to ground potential equalization conductor? What do you make of the Grounding passage below?

 

I opened it more than a year ago, took many pictures of different angles, and never opened it again because I don't want to damage any part.

It was initially approved for use in medical in the early 2010s but now it is no longer used for medical. That is why the product is now called g.USBamp Reseach in their website. Only for Research use. They said it was so expensive to pay for approval and since it is mostly used in BCI (Brain Computer Interface) project, then it is no longer approved for used in medical. In the following instruction for use in their other product. They are meant to use the potential equalization conductor to ground to earth. Maybe in transitioning from Medical to Research device, the original advisors are long gone so forgot to emphasize never to ground potential equalization conductor? What do you make of the Grounding passage below?

View attachment 354581

Legaly , and with the way you quote people on different post randomly and out of context , there is no way in going near making a statement on earthing equipment thats used on what you say is a brain computer interface , and is made by a company that undoutably has more lawyers than I do.

As I understand the regulations , it's how the equipment is used that determins what level of requirements you need to apply.

 

hi,
The TS clearly states:

It was initially approved for use in medical in the early 2010s but now it is no longer used for medical. That is why the product is now called g.USBamp Reseach in their website. Only for Research use.

Moderation

 

Legaly , and with the way you quote people on different post randomly and out of context , there is no way in going near making a statement on earthing equipment thats used on what you say is a brain computer interface , and is made by a company that undoutably has more lawyers than I do.

As I understand the regulations , it's how the equipment is used that determins what level of requirements you need to apply.

In the United States, one can't buy an EEG device unless one is a doctor or nurse. I tried to buy a Brainmaster product before but the company wouldn't sell me. You can't even buy one at EEGsales. But I was able to get a Brainmaster Atlantis II at Ebay. I was surprised the JTAG fuse was not burnt and I can read the firmware by interfacing to it. At that time. I planned to enhance the firmeware but I did't understand assembly language of the MPU401. I only know the 68HC11 assembly language which I used to modify their prototype Brainmaster 2E. Now all of them are just lying in the dusts in the cabinet. In UK. Can anyone buy an EEG device? I read EEG is less strict in the EU.

The new regulation of non-medical neurotechnologies in the European Union: overview and reflection - PMC

"Abstract
The regulation of neurotechnologies for non-medical purposes such as enhancement, gaming, or well-being is a topic of ongoing controversy. Without much attention, the European Union addressed it by two implementing regulations to the Medical Device Regulation (MDR) for non-invasive brain stimulation devices, passed in December 2022. This paper presents main aspect of these regulations and the conditions for placing non-medical neurodevices on the EU market, especially the risk threshold and the requirement for pre-market certification. It also provides a first critical comment on selected aspects and the unclear situation regarding research only devices which has alarmed the European neurotechnology sector."

Btw.. the following is g.USBamp application in the US. For other countries it is not required?

 

In the United States, one can't buy an EEG device unless one is a doctor or nurse. I tried to buy a Brainmaster product before but the company wouldn't sell me. You can't even buy one at EEGsales. But I was able to get a Brainmaster Atlantis II at Ebay. I was surprised the JTAG fuse was not burnt and I can read the firmware by interfacing to it. At that time. I planned to enhance the firmeware but I did't understand assembly language of the MPU401. I only know the 68HC11 assembly language which I used to modify their prototype Brainmaster 2E. Now all of them are just lying in the dusts in the cabinet. In UK. Can anyone buy an EEG device? I read EEG is less strict in the EU.

The new regulation of non-medical neurotechnologies in the European Union: overview and reflection - PMC

"Abstract
The regulation of neurotechnologies for non-medical purposes such as enhancement, gaming, or well-being is a topic of ongoing controversy. Without much attention, the European Union addressed it by two implementing regulations to the Medical Device Regulation (MDR) for non-invasive brain stimulation devices, passed in December 2022. This paper presents main aspect of these regulations and the conditions for placing non-medical neurodevices on the EU market, especially the risk threshold and the requirement for pre-market certification. It also provides a first critical comment on selected aspects and the unclear situation regarding research only devices which has alarmed the European neurotechnology sector."

Btw.. the following is g.USBamp application in the US. For other countries it is not required?



View attachment 354595

View attachment 354596

View attachment 354597

you say

" I planned to enhance the firmeware but I did't understand assembly language of the MPU401."

on a product you say

"In the United States, one can't buy an EEG device unless one is a doctor or nurse. I tried to buy a Brainmaster product before but the company wouldn't sell me. You can't even buy one at EEGsales. But I was able to get a Brainmaster Atlantis II at Ebay"

please dont before you injur or cause worse harm to people.

 

you say

" I planned to enhance the firmeware but I did't understand assembly language of the MPU401."

on a product you say

"In the United States, one can't buy an EEG device unless one is a doctor or nurse. I tried to buy a Brainmaster product before but the company wouldn't sell me. You can't even buy one at EEGsales. But I was able to get a Brainmaster Atlantis II at Ebay"

please dont before you injur or cause worse harm to people.

In 1999 I bought the Brainmaster 2E, but didn't used it the past 20+ years. Two years ago I got it from the attic and tried to run it, then their latest software bricked it by copying over some firmware memory areas. Then I tried to learn how to fix it since Brainmaster wouldn't fix it. I learnt the 68HC11 assembly language for 3 months from scratch extensively until I was able to repair the bricked firmware by supplying 3 missing lines. I bought the newer Brainmaster Atlantis after that after I saw a good deal at Ebay since it is more modern version. It's frequency limit is only up to 100Hz. I need at least 1000Hz cutoff. So tried to fix the firmware of the Atlantis to see if I can increase the cutoff, but I didn't have time to study the MPU401 assembly language. Then I saw the g.USBAMP which has cutoff of 2400Hz. And saw it at Ebay and so got it.

Anyway. I noticed something. Circuits in year 1999 were quite ancient with very big chps but in the year 2008 the circuits are very small and modern. In fact, the Brainmaster Atlantis II being sold now in year 2025 still used the original 2008 design. So is the g.USBamp which was designed in 2005 but they never upgrade it now in 2025 and it's selling like pancakes even if it is $17,700 and without any DRL circuit. Do you know why in 2008 the circuits of many devices become very advanced compared to year 1999? So many devices now still use the 2008 designs.

 

In 1999 I bought the Brainmaster 2E, but didn't used it the past 20+ years. Two years ago I got it from the attic and tried to run it, then their latest software bricked it by copying over some firmware memory areas. Then I tried to learn how to fix it since Brainmaster wouldn't fix it. I learnt the 68HC11 assembly language for 3 months from scratch extensively until I was able to repair the bricked firmware by supplying 3 missing lines. I bought the newer Brainmaster Atlantis after that after I saw a good deal at Ebay since it is more modern version. It's frequency limit is only up to 100Hz. I need at least 1000Hz cutoff. So tried to fix the firmware of the Atlantis to see if I can increase the cutoff, but I didn't have time to study the MPU401 assembly language. Then I saw the g.USBAMP which has cutoff of 2400Hz. And saw it at Ebay and so got it.

Anyway. I noticed something. Circuits in year 1999 were quite ancient with very big chps but in the year 2008 the circuits are very small and modern. In fact, the Brainmaster Atlantis II being sold now in year 2025 still used the original 2008 design. So is the g.USBamp which was designed in 2005 but they never upgrade it now in 2025 and it's selling like pancakes even if it is $17,700 and without any DRL circuit. Do you know why in 2008 the circuits of many devices become very advanced compared to year 1999? So many devices now still use the 2008 designs.

yet again, one question is answered, and you go off in a new direction.

please mark this as a closed question and feel free to start a new post about why chip / circuits change over the decades .
yes 30 odd years is a long time in the world of electronics .

 

yet again, one question is answered, and you go off in a new direction.

please mark this as a closed question and feel free to start a new post about why chip / circuits change over the decades .
yes 30 odd years is a long time in the world of electronics .

Before i closed. Pls tell me the right words to look or ask for earthless source medical supply bec i want to buy it to 2 reasons. 1. To test how much common mode noise can be produced and why the unit doesnt have DRL. 2. I will cut my original AC adaptor to see if there is a capacitor from live to ground. Because if there is and the unit is connected to ground. Then if the earth is not competent..the hot line can create ground fault and energize the unit case. And ill warn all users of it if that is the case. Also i deleted the internal parts photos already bec the company said they charge 500 Euro for repair of the $17700 item so i dont want to piss them off making them refuse repair in case i need one in future. How do i self close the thread?

 

How do i self close the thread?

Use the Report button to ask a moderator to close the thread.

 

Hi Secan,
Do you wish to have this Closed, as you intend to Create a new Thread for a change of Topic?

Moderation.