Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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


    User Avatar
    Homework Helper

    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


    User Avatar
    Science Advisor
    Homework Helper

    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook