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Desperately need your help!

  1. Feb 3, 2009 #1
    This question is on the operation of a CRT.

    In a heart rate monitor, the time base is a standard 0.40s/ms.
    The distance between adjacent peaks on the display is 1.25cm per heart beat.
    Calculate the time taken for one heart beat.

    Any help with this will be very much appreciated. I missed a few lectures due to illness and now I'm so behind. I don't even know where to start with this!!
     
  2. jcsd
  3. Feb 3, 2009 #2

    LowlyPion

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    Welcome to PF.

    I don't think I exactly understand your problem statement, because typically your oscilloscope will be given as time/div.

    Now if you had said .40s/div then that would indicate to me that you have a .5sec peak to peak, for 1 heart beat, or 60/.5 = 120 beats per minute.
     
  4. Feb 3, 2009 #3

    mgb_phys

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    You have copied this down wrong. The timebase must be time/distance, ie 0.4s/cm

    Then if you measure the distance on the screen (1.25cm) and you know how fast the trace is moving you can work out how many seconds the 1.25cm represents.
     
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