Engineering Im having trouble analyzing this circuit

[think4432]

I'm looking at this ECG circuit in particular and I am having trouble analyzing it...

The ECG circuit and the driven right leg circuit to cancel out the noise.

I am a little bit confused on what exactly the r1, the op amp and r2 do...

And the values that are generally given to build something like this...

Can anyone help me out here? In great detail... perhaps?

Thank youuu.

 

[berkeman]

I'm looking at this ECG circuit in particular and I am having trouble analyzing it...

The ECG circuit and the driven right leg circuit to cancel out the noise.

I am a little bit confused on what exactly the r1, the op amp and r2 do...

And the values that are generally given to build something like this...

Can anyone help me out here? In great detail... perhaps?

Thank youuu.

The upper two opamps form a differential amp for the sensed ECG/EKG voltage. The average of these two voltages are fed into the lower right inverting amp to actively force the common-mode voltage of the patient (Pt) to zero/ground. This helps to keep the voltages going into the differential amp opamps within the input common-mode range of the opamps.

It seems that another alternative might be to hard-ground the Pt. Can you see any advantages/disadvantages of using this circuit versus just hard grounding the Pt's right ankle?

 

[berkeman]

(Thread moved from EE to HH/Engineering)

 

[Xitami]

...It seems that another alternative might be to hard-ground the Pt. Can you see any advantages/disadvantages of using this circuit versus just hard grounding the Pt's right ankle?

Safety?AD620.PDF

 

[think4432]

The upper two opamps form a differential amp for the sensed ECG/EKG voltage. The average of these two voltages are fed into the lower right inverting amp to actively force the common-mode voltage of the patient (Pt) to zero/ground. This helps to keep the voltages going into the differential amp opamps within the input common-mode range of the opamps.

It seems that another alternative might be to hard-ground the Pt. Can you see any advantages/disadvantages of using this circuit versus just hard grounding the Pt's right ankle?

I understand the Driven Right Leg circuit thanks to your explaining to an extent, but why is the requirement of resistors in the places that they are placed necessary? And what values of these resistors would be suitable? High values for some? Low for others? I am not fully understanding how they contribute to the circuit... Also, if we are not grounding the patients right ankle, what are we grounding? I do not see the advantages/disadvantages of it...?

Also can you give me some insight on the ECG circuit with AD620 as well? After this one?

You have been great help for my understanding on the differential op amps!

Thank you in advance!

 

[think4432]

Safety?


AD620.PDF

Is this because if we did not do this, the circuit would produce a lot of leakage voltage?

 

[think4432]

Also the leg is grounded to obtain electrical voltage?A small voltage is set up across the electrodes by the hearbeat/pulse . This voltage is sensed by the sensor/electrode and is fed to the input of the amplifier. [From a little more research]

How does high pass and low pass filters play a role in this?

 

[Phrak]

Safety?

No.

The average voltage gradient in open air is about 200 volts over 6 ft height. There are extreme differences in potential, including AC potential from the lines between a pacient and equipment, even in a room. Your op amp with +/-6 volt rails is only equipped to deal with about 6 volts of this.

How do you design a sensor system that won't saturate your op amps inputs?