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116Re: question about safety testing

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  • Max Kargl
    Jan 17, 2001
      Note:the first part of this message is kept in german,
      as no project-related things are mentioned.

      Hi Jörg,

      1) da ich jetzt endlich etwas Zeit finde, möchte ich gern an den
      Nachbau der EEG-Schaltung gehen.Dazu hätte ich folgende Fragen:
      a) welches der vorliegenden(Egroups ?) Designs empfiehlst Du?
      b) hast Du EINE günstige Bezugsquelle für ALLE Komponenten, vor
      Allem aber für INA114 (von Deutschland nach Östereich pflegt
      man
      bis zu 40 DM Versandkosten zu berechnen!)?
      c) muß für die In-Circuit-Programmierung des Controllers das
      Board-
      Design modifiziert werden,welche Software ist verwendbar?
      d) Ist PC-seitig(Windows95,98,NT,Linux) schon irgendeine
      rudimentäre
      Software(Dll) vorhanden ?

      2) Cheap Electrodes:
      As my grandfather bought a PCE-Trainer (standalone
      biofeedback-device,measuring ultra slow (brain) potentials)with a

      set of headband electrodes included,which I was told on request
      was
      also used
      for EEG-measurements, it showed up that these are very simple made:
      the set consists of a 5cm rubber band which can be adjusted to fit
      any headsize.There are four 4 polished steel (nirosta) electrodes
      attached which are made of simple PRYM Snap-Buttons.On the

      outside the unshielded electrode cables which are bundled into
      a (bajonett-locked) 5 pin Din-Plug,can be clipped in.
      The set costs about 100 $ and can be easily rebuilt for about 5$.
      The electrode placement (for the purpose of ULP-measurement)
      is as follows 2 (GND)dorsal,distance about 10 cm at height of eyes,
      2 ventral,same distance,at temple-height.
      I guess for the EEG-Amplifier the AGND electrodes would be
      attached
      to the ears (with clips).
      Contact to the skin is established by applying saltless
      electrode-gel.

      (.Would it make sense to solder sheet silver to the electrode
      surfaces (and after that,chloriding them) for better results ?
      (.By the way,the cheap one-way electrode set (3M) of the same
      distributor is ment for EKG usage only.

      (.Also by the way- As the units case is sealed with superglue,
      I won't be able to take an analyzing glimpse at the circuit
      for the time it is under warranty (6 months), although I am
      eager
      to learn some secrets of DC-measurement.

      3) This point has also been discussed (but not answered) in the
      brainmaster newsgroup:

      Have you ever thought of using the pc's soundcard
      as high quality (16 Bit !) AD-converter ?

      I can imagine several obstacles:
      (a optical insulation would have to deal with analogue signals.
      (b don't know how much aditional noise will be produced.
      (c input decoupling of the soundcard could cut off low frequencies.
      (d As far as I understand (most?) SCs have a minimum
      adjustable sample frequency of about 8kHz,
      so maybe one would have to take only samples of the sample.
      (e the only DLL I know offers only a call which can not

      execute in the background.There exist several

      programs(shareware), which utilize the soundcard as realtime-
      oscilloscope but without sourcecode...
      I guess one would need some DMA-Coding(of which I have no idea)
      (f I don't think MS-DirectSound supports the required tasks.

      Greetings, Max
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