Grounding Policy

Thread Starter

y.j.mahajan1312

Joined Jul 19, 2017
6
Hello All,

I am currently designing an data acquisition system using TI's ADS1299 for sensing EMG signal from human body.
I have my prototype PCB ready and working as expected when powered using 6V battery.

However, when I try to power this board using 12V medical grade SMPS ( My circuits can operate with 6 to 15VDC power supply)- EMG signals show lot of noise. This noise is completely eliminated when I connect SMPS earth with my DC ground.

However, I am aware that connecting AC earth with Data acquisition system's ground can be harmful for the circuitry and especially to Human as i am sensing bio-potential here.

Can someone please explain what is the best and safest policy for grounding of SMPS powered Data Acquisition systems?
 

andrewmm

Joined Feb 25, 2011
1,497
Hello All,

I am currently designing an data acquisition system using TI's ADS1299 for sensing EMG signal from human body.
I have my prototype PCB ready and working as expected when powered using 6V battery.

However, when I try to power this board using 12V medical grade SMPS ( My circuits can operate with 6 to 15VDC power supply)- EMG signals show lot of noise. This noise is completely eliminated when I connect SMPS earth with my DC ground.

However, I am aware that connecting AC earth with Data acquisition system's ground can be harmful for the circuitry and especially to Human as i am sensing bio-potential here.

Can someone please explain what is the best and safest policy for grounding of SMPS powered Data Acquisition systems?
Hi

Assuming this is a commercial product, you are going to have to get this approved by an independently certified test house.
The rules for different countries are different, and in some cases contradictory !
I'd suggest you chat to the test house your going to want to use to ge a handle on all the different requirements.
 

Hymie

Joined Mar 30, 2018
976
Audioguru again is correct, using a linear medical grade PSU should solve the problem.

The safety standard for electrical medical equipment does not allow patient connected circuits to be connected to earth; the rationale being that it could provide a return path for another patient applied voltage.

The reason stringent limits for electrical body currents are within the medical standard is that the patient may be unconscious and not respond with the normal adverse (let go) reaction to an electric shock.
 
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