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How to record a signal outside of a physics lab?

  1. Nov 23, 2004 #1
    I am trying to set up an experiement to measure period doubling in a leaky tap. My plan was to just have a speaker input to a computer (through the com port I assume) to register drips into some container.

    My web searchs for how to wire the two wires from a speaker to any port on the copmuter have so far been fruitless. I was wondering if anyone here has ever set up an experiment hooked to their computer without labview and some sort of external card made specifically for the purpose. I am hoping to do this on the cheap. Maybe I should just get a microphone and plug it into the sound jack, but I am not sure how to take that signal to a nice data file I can look at with matlab or something.

    Any links/advice would be gratly appreciated.
  2. jcsd
  3. Nov 23, 2004 #2


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    Monitoring the parallel port would be much simpler, you could feed in a pulse for each event and have the software poll the pin you're using to find said events.

    A microphone or leads could be fed to a comparator and then maybe even a 555 monostable to generate a pulse long enough to capture with you're polling interval whose period should be at least half that of the pulse.

    Might be easier to find a way to process the .wav file from a mic in the sound card into a pulsed output file where you can set the criteria to determine when an event has occured.


  4. Nov 24, 2004 #3
    Yes, after spending some more time looking up pin diagrams, I realized the serial port is a digital port, requiring an analog to digital converter chip, and thus a bread board and vcc. I could scrounge those from some physics lab at school I'm sure, but wanted to keep this as simple as possible, so you are right. A microphone is the way to go. thnx for the link.
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