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How to build a circuit that allows for the live collection of ECG signals using the three lead set-up. Also, this module describes the filters used to remove noise from the signal. Since the ECG is a relatively low frequency signal, most of the high frequency noise can be filtered out. However, due to arm muscle movements, there will also be low frequency noise that will always remain with the signal.

Collecting ecg signal: hardware

Using the NI Elvis breadboard and data acquisition system, the ECG signal is collected from the three leads. Lead 1 is connected to the right arm, Lead 2 is connected to the left wrist and Lead 3 is connected to the right ankle (see Introduction: Building an ECG Based Diagnostic System for more information about lead placement). The diodes placed between the input leads and the rest of the circuit are to protect the patient from any backflowing current.

Ecg signal collection circuit

ECG signal collection circuit adapted from that of Radio Locman (www.rlocman.ru). The AD620 is used as a differential amplifier with a gain of ~7 in order to combine the electrical signals from each of the leads into one easily readable signal.

In NI LabVIEW, the Data Acquisition Assistant (DAQ Assistant) is used to collect the signal after preliminary band pass filtering. The data is sampled at a rate of 1 kHz. Our LabVIEW VI is available here .

Signal conditioning

Signal filtering is necessary to help isolate the frequencies found in the ECG signal from the noise. With a three lead system, the majority of the noise comes from the electrical activity in the muscles on the arm, or electromyography (EMG) noise. EMG signals are present in a wide frequency band which overlaps with the ECG signal in the lower frequencies. Therefore, with this set-up, it is impossible to completely remove EMG noise from the ECG signal. Therefore, it is helpful for the patient to relax and remain still while the data is being collected. In addition, 60 Hz noise is present from power line interference which also must be removed.

Analog band pass filter design

The first stage of filtering is an analog filter built onto the NI Elvis breadboard. It is a bandpass filter with cut-off frequencies of 0.5 and 150 Hz. This will help eliminate the high frequency noise from the muscles before the signal is greatly amplified.

Analog bandpass filter circuit diagram

Bode plot–Analog band pass filter

Digital filters using labview

Once the signal has been acquired by the DAQ Assistant into LabVIEW, it is processed by two additional filters and amplification of 100 times. The first filter is a band stop filter between 55 and 65 Hz to eliminate power line interference. A third order Butterworth (IIR) was used to implement this filter because it is low order and has a good frequency response for this signal.

Magnitude of the frequency response–Digital band stop filter

The second is a tenth order Butterworth low pass filter. The cutoff frequency of this filter is 80 Hz to further eliminate EMG noise. The ECG signal is located between 0.5 Hz and about 70-80 Hz depending on the individual.

Magnitude of the frequency response–Digital low pass filter

The resulting signal is displayed in real time in the graphical user interface, also designed in LabVIEW.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
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ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
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a perfect square v²+2v+_
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algebra 2 Inequalities:If equation 2 = 0 it is an open set?
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or infinite solutions?
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The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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ramon Reply
Kristine 2*2*2=8
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Differences Between Laspeyres and Paasche Indices
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No. 7x -4y is simplified from 4x + (3y + 3x) -7y
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J, combine like terms 7x-4y
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Asali
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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AMJAD
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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AMJAD
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Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
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after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
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how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
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Azam
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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the Beer law works very well for dilute solutions but fails for very high concentrations. why?
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Source:  OpenStax, Building an electrocardiogram (ecg) diagnostic system. OpenStax CNX. Dec 19, 2008 Download for free at http://cnx.org/content/col10620/1.1
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