You are welcome! Glad that you liked my EKG amplifier video. Here are a few more examples, Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html PhotoDiode Amplifier with Data Compression Explained ruclips.net/video/hqrRx2ufAwg/видео.html Thermometer Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html Thermometer Current source ruclips.net/video/Ggf0yCaTTiY/видео.html I hope these videos are interesting as well.
Glad that this video is interesting. And nice to hear that you are planning to experiment with his design. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
Thank you, Glad that you like my videos. For more sensor videos please see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj Hope it is interesting as well 🙋♂️
Common mode noise is captured and returned (re-injected) into the body but by a phase shift of 180° sort of speak to cancel out. Is it that? And then I guess the times 20 gain is to overcome various losses so it is approximately the same amplitude as the 0° original noise signal when it is in the body.
Yes, well-said. Common mode noise like 60Hz main power sinusoidal interference picked up by the body of patients can be further attenuated by as much additional 30 dB (basically improving CMRR or Common Mode Rejection Ratio) via the negative feedback applied to the leg in this example. The voltage gain of 20x in the feedback path is to attenuate the common mode interference or noise by 1/(1+20) in this system from input to the output.
Great video, but would you be able to suggest suitable values for the "input" resistors? My expectation is that the values might fall between 10k and 270k, similar to the "R_output" in the circuit. ...
Your are welcome! Glad that you like this EKG video. Yes, a nominal value of 100k Ohm is fine. I highly recommend checking your Op Amp data sheet regarding input impedance and offset requirements of your operational amplifier. For more sensor videos see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
I remember my brother hooking up the leads to my wrists and ankle when he was playing with his first EKG device fresh from med school. Is it too different to the one used to measure brain waves? Thanks for another great video!
You're welcome. Glad that you liked this ECG video and it brings back good memories. The one used to measure brain waves is the Electroencephalogram (EEG) used to measure the electrical activity of the brain, via electrodes applied to patient's scalp. More sensor videos are posted in ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj which is the the new Sensors Amplifiers playlist.
My pleasure, you're welcome! Glad that this video is useful. Yes, while signal conditioning and interfacing analog circuitry in commercial ECG devices are more complex with more components depending on the number of supported channels, at the core they have a similar instrumentation-like differential amplifier with negative feedback scheme in place to further improve CMRR from nominal -60 dB to -90 or -100 dB. The ECG signal is then digitized via A/D for further digital post processing and filtering in computer or dedicated signal processor. More sensor videos are posted in the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
Now, modern ECG use digital filter FIR or IIR by using software to filter out the AC noice or electrode artifact. But Op-Amp still need to learn as Medical Instrument 101. Modern ECG use IC as front end amplifier( circuit inside is the same but resistor on chip is trimed to make it more precision and less noice )
Thanks for your interest in this circuit video and for sharing your thoughts. Yes, these days there are ample choices in the form of integrated circuits (IC) for mixed signal interfacing with sensors.
I suggest a low noise Zero-Drift CMOS op amp from Texas Instruments or Analog Devices. TI's OPA4189 is a Quad OpAmp Chip that should be a good choice for this circuit. Additional choices are OPA4188 or Analog Devices LTC1151 www.ti.com/product/OPA4189 www.ti.com/product/OPA4188 www.analog.com/media/en/technical-documentation/data-sheets/1151fa.pdf I hope this is helpful.
Thank you for your interest in this ECG video. Regarding the Op Amp, I highly recommend using zero drift ultra low noise CMOS Op Amp from Texas Instrument or Analog Devices. For example AD8630 Zero Drift Quad Op Amp from Analog Devices or Texas Instrument's TLV4387 Quad, ultra-high-precision (10 μV) zero-drift (0.01 μV/°C) low-input-bias-current op amp.
You are welcome, Glad that you like this video. For more sensor videos please see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj Thank you 🙋♂️
An Electrocardiogram or ECG Amplifier with Right Leg Drive is explained in this video. For more sensor amplifiers see ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj and the following videos Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html PhotoDiode Amplifier with Data Compression Explained ruclips.net/video/hqrRx2ufAwg/видео.html Thermometer Circuit Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html Thermometer Current source ruclips.net/video/Ggf0yCaTTiY/видео.html Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html Temperature-Compensated Programmable Current Source Circuit Design with Zener Diode, BJT Transistors ruclips.net/video/QY48IQXJIRI/видео.html Temperature-Independent Current Circuit Design with Op Amp, BJT, Zener, Schottky Diodes ruclips.net/video/hFbnjbddUvs/видео.html Instrumentation Amplifier with Electronic Gain Control ruclips.net/video/C4tghZ-q6Zs/видео.html For more analog circuits and signal processing examples see: ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these sensors and thermometer circuits videos are interesting. 🙂
@@ЁбрагимИпатенкоибнАдхарма That's a good question. Generally speaking it is possible but with extra care because relative placement of ECG electrodes on arms and legs do matter to achieve proper measurement. So, it is important to follow specific procedure to make adjustments to the placement of the rest of electrodes if left leg drive is desired. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
@@behzadabf Thank you. Glad that you liked this ECG amplifier video. Here are a few more examples, Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html Thermometer Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html Hope that these videos are interesting as well.
Really good video sir, but I still have a hard time understanding why VO1=-VO2 , It implies that the potentials are always symmetrical, I've been looking for an explanation everywhere without success 😔
Thanks for watching and your good question. Starting my explanation at 13:01 in this video, I should've clearly mentioned that the virtual short of third op amp (feedback op amp) will enforce that its negative terminal (mid point between Vo1 and Vo2) have the same zero voltage as its grounded positive terminal as seen in the video. This results in mid point between Vo1 and Vo2 to be grounded and therefore in differential mode will result in Vo1 = -Vo2 since current flows from one Voltage to the other voltage through the resistors there are in between. I hope this further explanation answers your question. Here is another instrumentation amplifier video ruclips.net/video/9-MLqyewXW8/видео.html which explains a programmable Switched-Gain Instrumentation Amplifier.
@@STEMprof Thanks for your reply, I thought so, and also found that if we have the differential inputs v1 and v2 we would have vcm = (v1+v2)/2 and vd= v2 - v1, and by rearranging the 2 equations we have v1 = vcm - vd/2 and v2 = vcm + vd/2 which also leads us to the same conclusion.
Thank you! Glad that this video is interesting. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
Very informative and explained clearly. I learned a great deal from this video. Thanks!
You are welcome! Glad that you liked my EKG amplifier video. Here are a few more examples,
Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html
Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html
PhotoDiode Amplifier with Data Compression Explained ruclips.net/video/hqrRx2ufAwg/видео.html
Thermometer Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html
Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html
Thermometer Current source ruclips.net/video/Ggf0yCaTTiY/видео.html
I hope these videos are interesting as well.
Very cool, I will definitely build this circuit!
Glad that this video is interesting. And nice to hear that you are planning to experiment with his design. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
I like your videos which explain how its work.
Thank you, Glad that you like my videos. For more sensor videos please see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
Hope it is interesting as well 🙋♂️
I always wondered how they do it. Seeing the 3rd wire is what tickled me.
Glad that this video is helpful. More sensors related video are posted in ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj Playlist.
Common mode noise is captured and returned (re-injected) into the body but by a phase shift of 180° sort of speak to cancel out. Is it that? And then I guess the times 20 gain is to overcome various losses so it is approximately the same amplitude as the 0° original noise signal when it is in the body.
Yes, well-said. Common mode noise like 60Hz main power sinusoidal interference picked up by the body of patients can be further attenuated by as much additional 30 dB (basically improving CMRR or Common Mode Rejection Ratio) via the negative feedback applied to the leg in this example. The voltage gain of 20x in the feedback path is to attenuate the common mode interference or noise by 1/(1+20) in this system from input to the output.
This concept was make me very confuse while studied RL driver circuit. Untill the noise cancelling headphone widely sold.
Great video, but would you be able to suggest suitable values for the "input" resistors? My expectation is that the values might fall between 10k and 270k, similar to the "R_output" in the circuit. ...
Your are welcome! Glad that you like this EKG video. Yes, a nominal value of 100k Ohm is fine. I highly recommend checking your Op Amp data sheet regarding input impedance and offset requirements of your operational amplifier. For more sensor videos see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
I remember my brother hooking up the leads to my wrists and ankle when he was playing with his first EKG device fresh from med school. Is it too different to the one used to measure brain waves?
Thanks for another great video!
You're welcome. Glad that you liked this ECG video and it brings back good memories. The one used to measure brain waves is the Electroencephalogram (EEG) used to measure the electrical activity of the brain, via electrodes applied to patient's scalp. More sensor videos are posted in ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj which is the the new Sensors Amplifiers playlist.
Is it true that this circuit is used as the central part of industrial ECG machines?
Thanks for the video! It's very informative
My pleasure, you're welcome! Glad that this video is useful. Yes, while signal conditioning and interfacing analog circuitry in commercial ECG devices are more complex with more components depending on the number of supported channels, at the core they have a similar instrumentation-like differential amplifier with negative feedback scheme in place to further improve CMRR from nominal -60 dB to -90 or -100 dB. The ECG signal is then digitized via A/D for further digital post processing and filtering in computer or dedicated signal processor. More sensor videos are posted in the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
I see, thank you :)
Now, modern ECG use digital filter FIR or IIR by using software to filter out the AC noice or electrode artifact. But Op-Amp still need to learn as Medical Instrument 101. Modern ECG use IC as front end amplifier( circuit inside is the same but resistor on chip is trimed to make it more precision and less noice )
Thanks for your interest in this circuit video and for sharing your thoughts. Yes, these days there are ample choices in the form of integrated circuits (IC) for mixed signal interfacing with sensors.
I have a question, which commercial op amp could be selected for the common mode rejection circuit?
I suggest a low noise Zero-Drift CMOS op amp from Texas Instruments or Analog Devices. TI's OPA4189 is a Quad OpAmp Chip that should be a good choice for this circuit. Additional choices are OPA4188 or Analog Devices LTC1151
www.ti.com/product/OPA4189
www.ti.com/product/OPA4188
www.analog.com/media/en/technical-documentation/data-sheets/1151fa.pdf
I hope this is helpful.
Thank you for your interest in this ECG video. Regarding the Op Amp, I highly recommend using zero drift ultra low noise CMOS Op Amp from Texas Instrument or Analog Devices. For example AD8630 Zero Drift Quad Op Amp from Analog Devices or Texas Instrument's TLV4387 Quad, ultra-high-precision (10 μV) zero-drift (0.01 μV/°C) low-input-bias-current op amp.
that is interesting, thanks 💯🎉
You are welcome, Glad that you like this video. For more sensor videos please see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
Thank you 🙋♂️
An Electrocardiogram or ECG Amplifier with Right Leg Drive is explained in this video. For more sensor amplifiers see ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj and the following videos
Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html
Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html
PhotoDiode Amplifier with Data Compression Explained ruclips.net/video/hqrRx2ufAwg/видео.html
Thermometer Circuit Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html
Thermometer Current source ruclips.net/video/Ggf0yCaTTiY/видео.html
Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html
Temperature-Compensated Programmable Current Source Circuit Design with Zener Diode, BJT Transistors ruclips.net/video/QY48IQXJIRI/видео.html
Temperature-Independent Current Circuit Design with Op Amp, BJT, Zener, Schottky Diodes ruclips.net/video/hFbnjbddUvs/видео.html
Instrumentation Amplifier with Electronic Gain Control ruclips.net/video/C4tghZ-q6Zs/видео.html
For more analog circuits and signal processing examples see: ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt
I hope these sensors and thermometer circuits videos are interesting. 🙂
What happens if driving left leg?)
@@ЁбрагимИпатенкоибнАдхарма That's a good question. Generally speaking it is possible but with extra care because relative placement of ECG electrodes on arms and legs do matter to achieve proper measurement. So, it is important to follow specific procedure to make adjustments to the placement of the rest of electrodes if left leg drive is desired. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj
🙏perfect.
@@behzadabf Thank you. Glad that you liked this ECG amplifier video. Here are a few more examples,
Digital Stethoscope Microphone Amplifier Explained ruclips.net/video/ez5KtkPbsHg/видео.html
Thermometer Sensor Circuit Explained ruclips.net/video/5jmbZ9ak6EI/видео.html
Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html
Thermometer Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html
Hope that these videos are interesting as well.
Really good video sir, but I still have a hard time understanding why VO1=-VO2 , It implies that the potentials are always symmetrical, I've been looking for an explanation everywhere without success 😔
Thanks for watching and your good question. Starting my explanation at 13:01 in this video, I should've clearly mentioned that the virtual short of third op amp (feedback op amp) will enforce that its negative terminal (mid point between Vo1 and Vo2) have the same zero voltage as its grounded positive terminal as seen in the video. This results in mid point between Vo1 and Vo2 to be grounded and therefore in differential mode will result in Vo1 = -Vo2 since current flows from one Voltage to the other voltage through the resistors there are in between. I hope this further explanation answers your question. Here is another instrumentation amplifier video ruclips.net/video/9-MLqyewXW8/видео.html which explains a programmable Switched-Gain Instrumentation Amplifier.
@@STEMprof Thanks for your reply, I thought so, and also found that if we have the differential inputs v1 and v2 we would have vcm = (v1+v2)/2 and vd= v2 - v1, and by rearranging the 2 equations we have v1 = vcm - vd/2 and v2 = vcm + vd/2 which also leads us to the same conclusion.
You're welcome! Glad that the explanation was helpful.
Great!
Thank you! Glad that this video is interesting. For more sensor videos pls see the Sensors Amplifiers playlist ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj