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PC monitoring of a DC signal

Discussion in 'Electronic Basics' started by Bill Rule, Jun 25, 2004.

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  1. Bill Rule

    Bill Rule Guest

    I wonder if anyone out there has a sound no-frills way of monitoring
    either a 10mV or 2V DC signal (at approx 1 to 3 Hz)using
    shareware/freeware and taking the signal through either the Parallel
    port or a sound-card?

    Basic building of an appropriate black box wouldn't be beyond me, but
    this is to temporarily allow the output from a UV detector on an HPLC
    in a lab.

  2. Bob Masta

    Bob Masta Guest

    My Daqarta for DOS package will do this if you use the
    LPTX driver. You will need to build a simple 8-bit ADC
    from an R-2R ladder, which is driven by the LPT data port. The
    output of the ladder is combined with the input signal
    and applied to a pin on the LPT status port. The driver
    takes care of switching the ladder and watching the
    status bit to determine the input value. Depending
    upon your particular LPT port, you may be able to do
    this with just passive components. Worst case, you
    may need to add a digital buffer (74HC373) to make
    the data pins have equal drives. Schematics for both
    designs are in the LPTX.HLP file.

    Daqarta will allow you to monitor the signal in real-time,
    and optionally save it to a disk file.

    Sound cards don't go down to DC. If you want to use
    a sound card, you can apply your signal to a "chopper"
    to turn it into a square wave at a higher frequency
    (say, 1000 Hz) that the sound card can handle, then
    you can demodulate the envelope in software that
    you will have to write yourself. (I'm working on this,
    but it's a back-burner project.)

    Hope this helps!

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  3. the Wiz

    the Wiz Guest

    How about $25US for a serial-port powered multi-channel A/D converter with
    software? Click on the "Click Here" in the left column.

    It also includes an ActiveX control for interfacing your own Windows programs to
    the device (if you're a programmer ;-)

    More about me:
    VB3/VB6/C/PowerBasic source code:
    Freeware for the Palm with NS Basic source code:
    Drivers for Pablo graphics tablet and JamCam cameras:
    Email here:
  4. Bill Rule

    Bill Rule Guest

    Well, I guess I can't go past that for a deal... thanks to you both for the
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