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Questions tagged [biopotential]

Instrumentation related to the measurement of bioelectric phenomena from the living system, such as ECG, EEG, EMG, and galvanic skin response.

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Are these switches really necessary?

I'm analyzing the OpenBCI Ganglion board and I reasoned that switches SW1 through SW4 (part number CJS1200) might in fact be useless. The negative input for each channel (X_IN-) is connected via a ...
AlexanderCar's user avatar
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1 answer
82 views

How do the input current bias and the driven ground circuits in OpenBCI Ganglion work?

I am trying to understand how the OpenBCI Ganglion board works, but I can't figure out how these two sub-circuits work. I'm sorry I'm not too familiar with op-amps.
AlexanderCar's user avatar
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300 views

Effect of the placement of ground electrode on ECG

The above figure shows two ECG signals recorded after placing the positive electrode on the left palm and the negative electrode on the right palm. For the recording on the top column, the ground ...
hari's user avatar
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2 votes
5 answers
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Asking advice for designing an analog circuit with amplifiers

This is my first time trying to create a circuit by myself. I have been learning different combinations of circuits such as a differential amplifier, some kind of basic circuits with an operational ...
TSLee's user avatar
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3 votes
1 answer
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INA128: EMG signal output voltage shift when leg touch the ground

I followed this circuit to get the EMG signals (dual supply +-9 V). I set the Rg at 330 Ω (at 2.8 kΩ, I can't see any changes in the output, so i set the gain higher), and replaced OPA2131 with TL072 ...
MonhVuv Vu's user avatar
1 vote
2 answers
261 views

How does this EEG safety circuit work?

I'm trying to understand the following circuit, which I found in this document (on page 5). The purpose of the circuit is to go between a set of EEG electrodes and an EEG signal amplifier, and protect ...
Svedberg's user avatar
1 vote
1 answer
204 views

INA333 strange output, it's the same w/ and w/o input

This is the EOG (Electroencephalography circuit I'm working with) The output is essentially noise when I hook up the electrodes to myself, hence I'm debugging each stage, hooking up to an ...
roaibrain's user avatar
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1 answer
260 views

Voltage reference vs voltage bias for EOG circuit

This is continuation of my previous question. I'm confused about the reference voltage and bias voltage. As seen in the image above, the supplies for the INA333 and OPA2335 are clearly 3.3V and ground....
roaibrain's user avatar
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Instrumental amplifier outputs in 12 lead ECG [closed]

Currently we are trying to build 12 lead ECG circuit, so we just need to know the answers to couple of questions. Why do instrumental amplifiers on given circuit have two outputs? How are they ...
Nika Abashidze's user avatar
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1 answer
75 views

How to design gain based on input voltage and ADC voltage range?

What are the parameters to consider when designing gain amplification whether it be 2- or 1-stage (why one or the other?) when given an input and an ADC? I see for the same kind of signal (biosignal) ...
roaibrain's user avatar
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Calculate parameters of active high pass and low pass filter given for EOG circuit

The circuit is from here. The opamps are : OPA2335 (dual channel because of horizontal and vertical electrodes.) I don't exactly understand how to calculate R and C values based on the 0.5 high pass ...
roaibrain's user avatar
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1 answer
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3 electrode EOG system design

I'm trying to design an EOG system based on how the JINS MEME glasses did it. 3 electrodes, two on either side of the nose and one of the nose bridge. This will be battery powered. The expected ...
roaibrain's user avatar
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1 vote
3 answers
117 views

Which lead is the output when 3 lead ECG system is used?

I am using ECG signal conditioning chip called AD8232. It takes 3 inputs, namely, right arm (RA), left arm (LA) and Right leg (RL) & gives one analog output as the ECG signal. According to ...
Gagan G's user avatar
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1 answer
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Would grounded conductors placed on skin prevent signals from reaching a shielded body part?

Here is the scenario: You are in an environment where there are sources of EM signals that your body will pick up as though it were an antenna via capacitive coupling, i.e. what happens with the 50/...
Zacary Wengdom's user avatar
2 votes
0 answers
108 views

Any theoretical reference for empirical equation for estimating oxygen saturation (% SpO2 = 110 - 25*R)? [closed]

The empirical equation used to estimate % SpO2 is based on the observation that the ratio of the red and infrared light absorbed by arterial blood (represented by R in the equation) varies linearly ...
Jahir hussain's user avatar
3 votes
1 answer
415 views

How to eliminate the noise of this circuit?

I've built the following circuit on a PCB with reference to a TI's solution. I changed the gain of the INA to 10 and the gain of the A3 stage to 40. I also changed the cut-off frequency of the A4 ...
Jack Black's user avatar
2 votes
0 answers
235 views

Why am I barely able to read the voltage changes with this circuit?

I'm using this EMG sensor to measure the EMG signal from my bicep. However, I can barely read the voltage change from an oscilloscope when my muscle contracts - the output is a horizontal line of 1.5V ...
Jack Black's user avatar
1 vote
1 answer
620 views

What is the reference voltage of Vin- and Vin+ in this circuit?

I'm trying to make a PCB board to measure Electrocardiogram (ECG) signal. I have some doubts about the DC offset of the 2 input signals (\$V_{IN-}\$, \$V_{IN+}\$) with reference to analog ground. I ...
Jack Black's user avatar
-1 votes
1 answer
119 views

Is one RLD electrode enough for multichannel ECG acquisition system?

I am trying to design the multichannel ECG measuring device. My device has to acquire 3 signals at the same time. I have to use 6 electrodes to be able to measure those signals. My problem is each ...
nizar dhahri's user avatar
6 votes
2 answers
7k views

How does a driven right leg work?

A driven right leg (DRL) circuit is often added to a biopotential amplifier to reduce the common mode voltage (i.e. to increase the common mode rejection ratio, CMRR). A basic form of biopotential ...
David Cian's user avatar
3 votes
2 answers
1k views

Is it valid to use transistors to route signals through the circuit?

I'm working on an ECG/EMG circuit and instead of duplicating the input, I've used transistors to route the signal to a specific in-amp depending on the user's selection. This is what I came up with: ...
Moe's user avatar
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How does carbon paste (graphite) interact with other conductors?

I am running a half-cell battery configuration. I am using carbon paste (graphite) as a trace (jumper) because my solution contains bio-materials and carbon is bio-friendly. The carbon paste is coated ...
Anwar Elhadad's user avatar
29 votes
3 answers
9k views

Can an oscilloscope be used as an EKG?

I was at my doctor's office and noticed an EKG machine that looked like a standard oscilloscope. In fact, its case was almost identical to my dual channel Tektonix 1104b. The main difference was that ...
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How to compute electric field between constantly changing potentials (LFP data)

I have a set of LFP (local field potential) data, which is basically the voltage of different points in the brain at different times. I would like to calculate the electric field at these points at ...
Minu Bahrami's user avatar
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1 answer
280 views

Differential Square Current generator LTspice

I am trying to model a square wave differential current generator in LTSpice for MAX30001 IC, refer page 6 for the specs. Specifications: Differential Square wave, Amplitude : 8 to 96 uApk and ...
seeker's user avatar
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3 votes
1 answer
418 views

Bio-impedance circuit inputs

Recently, I wanted to build a replica of a bio-impedance circuit that I found in one of the NIH.gov papers. As obvious, bio-impedance circuits are usually used to measure body composition. They are ...
ast5jx's user avatar
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1 vote
3 answers
249 views

Switching between low voltage recording of biologic signal, to high voltage stimulation

I am recording a biopotential signals (EEG ~microvolts), which I pass to a digital amplifier circuit (ADS1299). I am recording 8 channels. I would like to switch channels, one by one, with a voltage-...
Tom Foutz's user avatar
2 votes
1 answer
252 views

Voltage / amperage / setup for tingling sensation

There are small pens (powered by a single or double 1.5V battery) or other medical devices that upon touching your skin produce a tingling sensation. Main question: I wonder to what voltage, amperage ...
Alex's user avatar
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1 answer
565 views

How to compare performace of EMG electrodes?

I'm working on building an acquisition system for sEMG signals. The problem I'm facing is how can I reliably measure the performance of different designs? Obviously I can just put the electrodes to my ...
mactro's user avatar
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1 answer
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can you have a system with multiple anodes connected to one cathode (e.g.Battery, generator, biocell, solar cell)?

simulate this circuit – Schematic created using CircuitLab Usually, the anode transfers electrons to the cathode. However, let's say the anode is not releasing enough electrons to create enough ...
Anwar Elhadad's user avatar
1 vote
0 answers
54 views

How to control the potential in multiple-electrodes (3 or more) in electrochemical cells?

Usually, in most cell designs, the concept of two-electrode design is the baseline. The two electrodes are anode and cathode where the electron transfer happens between them. However, I have been ...
Anwar Elhadad's user avatar
0 votes
3 answers
600 views

Multiplexing analog signals

I am designing a system to measure voltages from bio-potential sources and feed them into an ADC after filtering and amplification. The source has the following charactristics: amplitudes are in 10's ...
NeuroEng's user avatar
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1 vote
3 answers
95 views

Noise in an unconnected biopotential electrode lead wire

My question stems from a particular statement on page 256 of the textbook Medical Instrumentation - Application and Design, Fourth Edition (by J. Webster): Relatively high potentials can often be ...
apollo901's user avatar
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3 answers
59 views

Recording sensory nerve action potentials at the skin surface without electrical stimulus

I studied many nerve conduction studies. In these studies, there is one stimulator that excites the nerve and there are electrodes placed at the skin surface on the path of the nerves to record the ...
Nishant Kathpal's user avatar
1 vote
2 answers
606 views

How many / which electrodes should I use as input for an RLD (right leg drive)?

When reading through the datasheet of the ADS1298 (an analog Front-End for Biopotential Measurements) I noticed the schematic on page 42 (see below): It is possible to select or deselect the positive ...
jusaca's user avatar
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1 vote
1 answer
48 views

Servo drive in biopotential amplifier

I have to design a bio potential measurement system: AD converter and the connecting digital / software part an analog amplifier stage: basically a regular ECG amplifier composed of discrete ...
moravas8051's user avatar
2 votes
2 answers
299 views

Hand contacting op amp photodiode circuit causes interference - what ist the physic behind it?

I am new to analogue electronics and I am still learning about op-amps. I use the most common circuit for amplifying a photodiode's signal to measure it with an ADC: Amplification gain is 1M, the ...
Dommar92's user avatar
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0 answers
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Whenever two system or sources are coupled they should have same current sink or common reference point (say ground). How to realize this in ECG?

Electrode (Ag-AgCl) are placed at different part and directly fed to positive and negative input of differential amplifier. How can we realize human body and amplifying system have same current sink ...
Prabal Devkota's user avatar
14 votes
4 answers
3k views

Why would you put your input amplifier in front of your filtering for an ECG signal?

In this article at eetimes.com they show the signal chain for measuring an ECG. The raw signal of an ECG contains noise and offsets at least a magnitude larger than the real signal. (Some few mV ...
jusaca's user avatar
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1 vote
1 answer
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Modify the AD8232 chip configuration to use only LEFT and RIGHT arm in steel leads configuration

I am an industrial designer (little experience with electronics) trying to modify one of the AD8232 chip configurations. The AD8232 is a Single-Lead, Heart Rate Monitor Front End. In the datasheet, ...
Kevin Mamaqi's user avatar
8 votes
5 answers
3k views

Circuit for small level voltage detection (microvolts)

I have been working on a project lately which help in the detection myogenic potentials (of the levels of micro-volts). After studying from several places, I finalized the following test circuit. The ...
DodZi's user avatar
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2 votes
1 answer
161 views

Direct signal injection from function generator for EEG BCI calibration

I have seen several topics related to calibration of BCI and most of them use a "head phantom". But I want to know, is it possible to test the openBCI hardware directly using function generator? And I ...
Zahi Azmi's user avatar
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1 vote
1 answer
528 views

Can ECG electrodes be used for EEG detection?

Im having financial limitation for purchasing EEG monitoring modules or electrodes. But so is not the case for ECG. I am doubtful whether I can use ECG electrodes for EEG since brainwaves are in the ...
user183710's user avatar
1 vote
2 answers
238 views

Are electrodes mostly homogeneous or are there variations by usage, such as EEG vs EKG/ECG?

Are electrodes mostly homogeneous or are there variations by usage? My main usage is EEG. I have some interests in other areas and see similar electrodes sold for less money when marketed for ...
Hack-R's user avatar
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1 vote
2 answers
756 views

Why is bipolar EMG better than monopolar at reducing (common mode) noises?

As defined in this post, the monopolar EMG can reduce the common mode noise by taking the difference of the two inputs, i.e. EMG_mono = k * (V1 - V2). And, for bipolar mode,EMG_bi = k3 * [k1 * (V1 - ...
Ray's user avatar
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0 votes
1 answer
105 views

Testing the integrity of cable shielding for suitability

I am currently working with an ECG cable, is there a way for me to test the integrity of the shielding of the cable without using it directly on an ECG monitor to check for interference.
msa12's user avatar
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-2 votes
1 answer
2k views

Is it possible to make a lightbulb light up by wetting your hands? [closed]

I was recently watching an Electroboom video on free energy devices, but my question is not about any of that stuff. Here's the video. At about 5:50 he claims and seemingly shows that he can light up ...
Tom's user avatar
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0 votes
1 answer
4k views

Is there any difference between AD620 vs INA128?

I'm trying to make an EMG sensor. I've found some tutorials, for example, DIY muscle sensor/EMG circuit for a microcontroller, but my main question is can I make an EMG sensor using AD620 instead of ...
Parsa's user avatar
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0 votes
2 answers
196 views

Recording of sensory nerve evoked potential generated through skin-receptors [closed]

If we touch / give pressure to a skin, there are many mechano-receptors like meissner/pacinian corpuscles that produce action potential in neurons. I am in a need to detect those action potentials ...
Nishant Kathpal's user avatar
5 votes
2 answers
672 views

Does anyone have advice on homemade EKG/ECG leads?

I'm not sure this is where it should be posted, so apologies in advance, but I'm working with an Arduino and Sparkfun's heart rate monitor AD8232 (https://www.sparkfun.com/products/12650) to gather ...
Asinine's user avatar
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