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 === The Biosignal How-To === === The Biosignal How-To ===
  
-[[http://​hackaday.com/​2016/​08/​23/​all-about-biosignals/​ | We have been featured on Hackaday: All About Biosignals ]] {{:logo.png?​nolink&​20|}} +{{:cover2.jpg|}}
  
-{{ :​image39_crop.jpg?200}}+This page shows you with the help of YouTube clips how to measure heart activity (ECG), brain waves (EEG), muscle activity (EMG) and other bio-signals.
  
-This page shows you with the help of YouTube clips how to build bio-amplifier and how to use it to measure ECG, EEG, EMG and other bio signals.+You will also learn how to to distinguish noise from actual biosignals and will see that often noise is "​sold"​ as biosignal. These clips will help you to critically evaluate these claims ​and make up your own mind.
  
-Besides the hands-on approach in amplifier design you will learn how to to distinguish noise from actual biosignals and will see that often noise is "​sold"​ as a biosignal, even in top level publicationsWith the help of these clips you can critically evaluate such results ​and make up your own mind.+[[https://​www.youtube.com/​c/​BPMbiosignals | Check out our YouTube channel for additional videos ​and playlists.]]
  
 +== ECG ==
 +| [[ecg:​einthoven|The Einthoven leads and the mean electrical axis]] | [[ecg:​einthoven|{{:​vasso_eithoven.jpg}}]] |
 +| [[ecg:​avflr|The augmented limb leads aVF, aVR and aVL]] | [[ecg:​avflr|{{:​image5thumb.png}}]] |
 +| [[ecg:​heart_axis_vector_ecg|The electrical heart axis and the vector ECG]] | [[ecg:​heart_axis_vector_ecg|{{:​vectthumbnail.jpg}}]] |
 +| [[ecg:​v1_v6|The chest leads V1,...,V6]] | [[ecg:​v1_v6|{{:​image8_crop_sc.png}}]] |
 +| [[ecg:​gndamp|The GND or N electrode]] | [[ecg:​gndamp|{{:​biosig_gnd.00_00_44_12.still004_thum.jpg}}]] |
 +| [[ecg:​artefacts|ECG artefacts]] | [[ecg:​artefacts|{{:​image3_thumb.jpg}}]] |
 +| [[ecg:​cheststrap|Chest strap ECG]] | [[ecg:​cheststrap|{{:​chest_strap_thumb2.jpg}}]] |
 +| [[ecg:​hrv|Heart Rate Variability]] | [[ecg:​hrv|{{:​hrv_thumb.jpg}}]] |
  
-=== The circuit diagram of the bio-amplifier === 
-{{:​full_amp_w_inp_prot.png|}} 
  
-The bio-amplifier is a two stage amplifier. The first stage is an instrumentation amplifier and the second stage is a standard non-inverting OP-ampBetween the first and second stage is a highpass filter which removes any DC generated by the electrodes. ​For that reason the gain of the instrumentation amplifier is kept low not to be driven into saturation. The highpass filter usually has a cutoff frequency in the region of 1 - 0.1Hz depending on the signals measured.+== EEG == 
 +| [[eeg:​alpha|Measuring alpha waves from the visual cortex]] | [[eeg:​alpha|{{:​image7thumb.jpg}}]] | 
 +| [[eeg:​artefacts|EEG artefacts]] ​ | [[eeg:​artefacts|{{:​smiling_eeg_thumb.jpg}}]] | 
 +| [[eeg:​dryelectrodes|Recording EEG with dry electrodes]] | [[eeg:​dryelectrodes|{{:​dry_thumb.jpg}}]] | 
 +| [[eeg:​vep|Visually evoked potentials]] | [[eeg:​vep|{{:​image9thumb.jpg}}]] |
  
-=== Or do you want to buy an assembled bioamp instead to focus on the ECG/EEG/EMG experiments?​ === 
  
-For those who are too scared of a soldering iron... [[http://www.attys.tech We've made fully tested and CE marked bioamp which is called "​ATTYS"​.]] Vasso Georgiadou, our main presenter explains how it works (and why it's called Attys):+=== Non electrical biosignals === 
 +| [[nonelec:​acceleration | Acceleration (vs EMG)]] | [[nonelec:​acceleration|{{:​acc.jpg}}]] | 
 +[[nonelec:pulse | Light (to detect pulse)]] | [[nonelec:​pulse|{{:​pulseoxy.jpg}}]] ​| 
 +| [[nonelec:​smoking | Temperature (while smoking ​cigarette)]] | [[nonelec:​smoking|{{:​temperature.jpg}}]] 
 +| [[nonelec:​pressure | Pressure ​(blood pressure)]] | [[nonelec:pressure|{{:​pressure.still002_sc.jpg}}]] | 
 +| [[nonelec:​sound | Sound (heart-sounds,​ Korotkov sounds, ultrasound)]] | [[nonelec:​sound|{{nonelec:​sound_thumb.jpg}}]] |
  
-[[http://​www.attys.tech ​www.attys.tech]]+=== Processing the data with MATLAB or OCTAVE === 
 +For offline data processing MATLAB and its free version OCTAVE are very easy to use.  
 +Here we show how to plot an ECG, its spectrum and how to remove 50 Hz mains noise from it. The same can also be done with EEG, 
 +EMG, etc: 
 +  - [[octave:plot|Plotting the raw data]] 
 +  - [[octave:​ecgplot|Plotting the data in proper units]] 
 +  - [[octave:​spectrum|Plotting the frequency spectrum]] 
 +  - [[octave:​50hzremoval|Removing 50Hz mains from the signal]] 
 +  - [[octave:​heartrate|Heart-rate detection]]
  
-{{youtube>​f2gCcIcOhhI}} 
  
-The Attys follows the same approach as shown on this page, namely ​two stage amplification but does the highpass filtering ​and 2nd stage amplification in softwareEven that it's ready made you can still change all filter ​parameters in softwareAll [[http://​www.attys.tech/​software/​ | software]] is open source so you can learn how it's done in digital and then hack the code to write your own applications. The Attys has software for general purpose data recording (AttysScope),​ ECG (AttysECG) and EEG (AttysEEG).+=== Build your own bio-amplifier === 
 +{{:​full_amp_w_inp_prot.png|}} 
 + 
 +The bio-amplifier is a two stage amplifier. The first stage is an instrumentation amplifier ​and the second ​stage is a standard non-inverting OP-ampBetween the first and second stage is a highpass ​filter ​which removes any DC generated by the electrodesFor that reason ​the gain of the instrumentation amplifier is kept low not to be driven into saturation. The highpass filter usually ​has a cutoff frequency in the region of 1 - 0.1Hz depending on the signals measured.
  
  
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   * [[http://​uk.farnell.com/​|Farnell]] have a really good product selection tree so that you find your components quickly. The order codes can directly be copy/pasted into their Product Search form at the top of the page.   * [[http://​uk.farnell.com/​|Farnell]] have a really good product selection tree so that you find your components quickly. The order codes can directly be copy/pasted into their Product Search form at the top of the page.
   * [[http://​uk.rs-online.com|RS]] will provide you also with all components but the web page is a bit more cumbersome.   * [[http://​uk.rs-online.com|RS]] will provide you also with all components but the web page is a bit more cumbersome.
-  * [[http://​www.maplin.co.uk/​|MAPLIN]] is good for standard components such as opamps, capacitors, resistors, etc. and you can actually hold the components in your hand before you buy them. 
-  * [[http://​www.ti.com/​|Texas Instruments]] might send you a free sample of their instrumentation amplifier. Give it a go. 
  
  
-=== Assembling ​the bio-amplifier ===+=== Assembly of the bio-amplifier ===
 I show you step by step how to do it. Component by component. I show you step by step how to do it. Component by component.
 First, we assemble the 2nd stage amplifier which is a non inverting OP-amp at a gain of G=100. First, we assemble the 2nd stage amplifier which is a non inverting OP-amp at a gain of G=100.
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   - [[noninvopamp:​groundtrack|Soldering the ground tracks]]   - [[noninvopamp:​groundtrack|Soldering the ground tracks]]
   - [[noninvopamp:​1Mpulldown|Fitting the 1M pulldown resistor at the non-inverting input (R9)]]   - [[noninvopamp:​1Mpulldown|Fitting the 1M pulldown resistor at the non-inverting input (R9)]]
-  - [[noninvopamp:​piezo|Testing the amplifier with a signal from a piezo headphone]] 
   - [[noninvopamp:​usbdux|Connecting the amplifier to the USB-DUX and using it as an oscilloscope]]   - [[noninvopamp:​usbdux|Connecting the amplifier to the USB-DUX and using it as an oscilloscope]]
  
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   - [[instramp:​power|Soldering the power connections]]   - [[instramp:​power|Soldering the power connections]]
   - [[instramp:​bananaplugs|Connecting the electrodes (X1,​X2,​X3)]]   - [[instramp:​bananaplugs|Connecting the electrodes (X1,​X2,​X3)]]
-  - [[instramp:​testingemg|Testing the bio amp: recording muscle activity (EMG)]] 
   - [[instramp:​inputprotection|Input protection and final assembly]]   - [[instramp:​inputprotection|Input protection and final assembly]]
  
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 [[conclusionvideo|watch this clip which explains in general how to measure any electrical bio-signal]]. [[conclusionvideo|watch this clip which explains in general how to measure any electrical bio-signal]].
  
-=== Using the bio-amplifier === 
  
-These sections show you that you can use the same amplifier to record ECG, EEG and EMGBesides showing you +=== Advanced: less analogue circuitry and more digital signal processing === 
-how it's done we have a strong focus on the artefacts generated so that you can critically assess your own recordings and those of others. The section about non-biological signals gives you pointers to other biosignals and also shows in comparison with electrical signals that they are often much more reliable.+When using a sigma delta converter with a high resolution ​you can do the highpass filtering ​and second stage amplification in software[[http://​www.ti.com/​lit/​an/​sbaa160a/​sbaa160a.pdf | This excellent application note describes ​it in detail.]] Our ready made bio amp 'Attys' also uses this approach.
  
-[[https://​github.com/​berndporr/​comedirecord | The oscilloscope program "​comedirecord"​ was used 
-for all recordings.]] 
  
-== ECG == +=== Attys ===
-| [[ecg:​einthoven|The Einthoven leads and the mean electrical axis]] | [[ecg:​einthoven|{{:​vasso_eithoven.jpg}}]] | +
-| [[ecg:​avflr|The augmented limb leads aVF, aVR and aVL]] | [[ecg:​avflr|{{:​image5thumb.png}}]] | +
-| [[ecg:​heart_axis_vector_ecg|The electrical heart axis and the vector ECG]] | [[ecg:​heart_axis_vector_ecg|{{:​vectthumbnail.jpg}}]] | +
-| [[ecg:​v1_v6|The chest leads V1,...,V6]] | [[ecg:​v1_v6|{{:​image8_crop_sc.png}}]] | +
-| [[ecg:​artefacts|ECG artefacts]] | [[ecg:​artefacts|{{:​image3_thumb.jpg}}]] | +
-| [[ecg:​hrv|Heart Rate Variability]] | [[ecg:​hrv|{{:​hrv_thumb.jpg}}]] |+
  
 +For those who are too scared of a soldering iron... [[http://​www.attys.tech | We've made a fully tested and CE marked bioamp which is called "​ATTYS"​.]] Vasso Georgiadou, our main presenter explains how it works (and why it's called Attys):
  
-== EEG == +[[http://www.attys.tech www.attys.tech]]
-[[eeg:alpha|Measuring alpha waves from the visual cortex]] | [[eeg:​alpha|{{:​image7thumb.jpg}}]] | +
-| [[eeg:​artefacts|EEG artefacts]] ​ | [[eeg:​artefacts|{{:​smiling_eeg_thumb.jpg}}]] ​| +
-| [[eeg:​dryelectrodes|Recording EEG with dry electrodes]] | [[eeg:​dryelectrodes|{{:​dry_thumb.jpg}}]] | +
-| [[eeg:​vep|Visually evoked potentials]] | [[eeg:​vep|{{:​image9thumb.jpg}}]] |+
  
 +{{youtube>​f2gCcIcOhhI?​small&​rel=0 }}
  
-=== Non electrical biosignals === +The Attys follows the same approach as shown on this page, namely two stage amplification but does the highpass filtering and 2nd stage amplification in software. Even that it's ready made you can still change all filter parameters in software. All [[http://​www.attys.tech/​software/ ​software]] is open source so you can learn how it's done in digital and then hack the code to write your own applicationsThe Attys has software for general purpose data recording ​(AttysScope), ECG (AttysECGand EEG (AttysEEG).
-[[nonelec:acceleration ​Acceleration (vs EMG)]] | [[nonelec:​acceleration|{{:​acc.jpg}}]] | +
-| [[nonelec:​pulse | Light (to detect pulse)]] | [[nonelec:​pulse|{{:​pulseoxy.jpg}}]] | +
-| [[nonelec:​smoking | Temperature ​(while smoking a cigarette)]] | [[nonelec:​smoking|{{:​temperature.jpg}}]] | +
-| [[nonelec:​pressure | Pressure ​(blood pressure)]] | [[nonelec:​pressure|{{:​pressure.still002_sc.jpg}}]] | +
-| [[nonelec:​sound | Sound (heart-sounds,​ Korotkov sounds, ultrasound)]] | [[nonelec:​sound|{{nonelec:​sound_thumb.jpg}}]] |+
  
-=== Processing the data with MATLAB or OCTAVE === 
-For offline data processing MATLAB and its free version OCTAVE are very easy to use.  
-Here we show how to plot an ECG, its spectrum and how to remove 50 Hz mains noise from it. The same can also be done with EEG, 
-EMG, etc: 
-  - [[octave:​plot|Plotting the raw data]] 
-  - [[octave:​ecgplot|Plotting the data in proper units]] 
-  - [[octave:​spectrum|Plotting the frequency spectrum]] 
-  - [[octave:​50hzremoval|Removing 50Hz mains from the signal]] 
-  - [[octave:​heartrate|Heart-rate detection]] 
  
- 
-=== Advanced: Do you want to have less analogue circuitry and do more DSP? === 
-When using a sigma delta converter with a high resolution (such as the [[http://​www.linux-usb-daq.co.uk/​prod2_duxsigma/​ | USB-DUX sigma]]) you can do the highpass filtering and second stage amplification in software. [[http://​www.ti.com/​lit/​an/​sbaa160a/​sbaa160a.pdf | This excellent application note describes how it can be done using a minimal amount of analogue components.]] Our ready made bio amp '​Attys'​ also uses this approach where the highpass filtering is done by a digital filter in the application software. 
  
  
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   * [[http://​www.linux-usb-daq.co.uk/​howto2/​eeg|A complete bioamp design with SMD components]]   * [[http://​www.linux-usb-daq.co.uk/​howto2/​eeg|A complete bioamp design with SMD components]]
   * [[http://​eu.wiley.com/​WileyCDA/​WileyTitle/​productCd-0471676233.html| Design and Development of Medical Electronic Instrumentation:​ A Practical Perspective of the Design, Construction,​ and Test of Medical Devices]]   * [[http://​eu.wiley.com/​WileyCDA/​WileyTitle/​productCd-0471676233.html| Design and Development of Medical Electronic Instrumentation:​ A Practical Perspective of the Design, Construction,​ and Test of Medical Devices]]
-  * [[http://​hackaday.com/​2016/​08/​23/​all-about-biosignals/​ | We have been featured on Hackaday: All About Biosignals ]] {{:​logo.png?​nolink&​20|}} ​ 
   * [[http://​en.wikipedia.org/​wiki/​The_Art_of_Electronics|The Art of Electronics]]   * [[http://​en.wikipedia.org/​wiki/​The_Art_of_Electronics|The Art of Electronics]]
   * [[http://​www.attys.tech| Attys, our assembled and tested bioamp you can buy]]   * [[http://​www.attys.tech| Attys, our assembled and tested bioamp you can buy]]
 +
 +[[http://​hackaday.com/​2016/​08/​23/​all-about-biosignals/​ | We have been featured on Hackaday: All About Biosignals ]] {{:​logo.png?​nolink&​20|}} ​
 +
start.1511210067.txt.gz · Last modified: 2017/11/20 20:34 by berndporr