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Body Sensor Network

When exploring novel processing methods applied on different kinds of biosignals, it is invaluable to resort to a configurable system which allows for easy recordings of unique measurements. 

Conducting laboratory experiments poses strict requirements to the sensors and its' hardware which are listed below 

  • Easy Applicability (Start/Stop measurements)
  • Synchronous measurements of numerous sensors
  • Battery driven modules suited for unobstrusive long-time measurements
  • Robustness (prevent or at least detect loss of data)
  • Standardized Data Formats (FAT Filesystem, EDF+ format support)
  • Modularized composition of Hardware and Firmware

Each sensor node is based on the same technical structure which is depicted in the following blockdiagram below.

Blockdiagram - rBSN Module
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Sensors - rBSN_HeartCore

The electrocardiogram (ECG) belongs to one of the most important biosignals that provide valuable indications of the cardiovascular system.

Therefore, a novel 12-lead ECG module is currently developed, designed to be used in laboratory and ambulatory settings. With regards to the hardware layout and analog preprocessing, special care has been taken to ensure a good signal quality as possible.

The main features are 

  • 12-lead Body Surface ECG (Einthoven I-III, precordial chest leads V1-V6)
  • Active Electrodes incorporating active preprocessing and filtering circuits
  • Integration of a 3-axis acceleration sensor on each electrode
  • Wireless Synchronization with other sensor nodes
  • Sampling rates up to 1kHz
  • Battery life for more than 48 hours
  • Wireless Data Streaming to external devices (Laptops, Tablets, Smartphones,...)
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Sensors - rBSN_DualPulseOximeter

The Photoplethysmogram (PPG) is another important biosignal, which is easily applicable in wearable Home-Monitoring-Systems and has become an indispensable part of routine medical applications. It was shown that non-invasive measurements of the PPG provide valuable information concerning pulse rate and pulse wave velocity, oxygen saturation and respiratory activity. Moreover, it can used to derive general indications of the cardiovascular bed like arterial elasticity and aging.

In the scope of the rBSN System, a novel PPG sensor has been developed, which supports both, transmissive as well as reflexive measurements. The transmissive finger clip is equipped with 5 LEDs of different wavelengths and three axis accelerometer that provides local information of the finger movements.

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Sensors - rBSN_EDA

The electrodermal activity (EDA) is assessed by measuring the electrical conductance of the skin (e.g. at the palm). As sweat is controlled by the sympathetic nervous system, skin conductance can be used as an indication of psychological or physiological arousal. Thus, it is an important measure for applications like emotion recognition or stress detection.

The main features are:

  • Battery life for more than 48 hours
  • 12 Bit ADC
  • Sample rate up to 8kHz
  • Resolution of skin conductance: 0.005µS (0-20µS)
  • Resolution of acceleration 0.0027g (+/- 3g)
  • 16 Bit MSP430 LowPower Microcontroller (TI)
  • Signal preprocessing on sensor node
  • Wireless time synchronization within BSN
  • Wireless data streaming to external devices (laptops, tablets, smartphones,...)
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Sensors - rBSN_MiniActimeter

Acquiring acceleration data has proven a valuable means in the different fields of biomedical signal processing. Gait analysis, restless leg syndrome observation,  sleep stage recognition, estimation of sleep wake model parametersor fall detection are typical applications where acceleration (ACC) signals are used to recognize specific patient movements.

In almost all applications, an unobtrusive data acquisitiondevice is desired, which next to easy applicability, high performance and reliable robustness also guarantees low power consumption and moderate production costs. As existing Actimeters often lack mass storage capabilities to record raw data or are restricted by their size, a new acceleration sensor meeting the aforementioned requirements has been developed, that allows continuous measurements of 3-axis acceleration data sampled at 500 Hz for at least 48 hours.

The layout was limited to a 30mm x 30mm PCB which gives just enough room to hold three ZA 675 Zink-Air button cell batteries.

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