Signal Conditioning - data acquisition

Discussion in 'The Projects Forum' started by Chogy, Feb 25, 2009.

  1. Chogy

    Thread Starter New Member

    Feb 25, 2009
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    0
    Hello everybody! I thought I could handle this project without too much help, but obviously that's not the case, thus my 1st post here.

    I am setting up a notebook PC for data acquisition: specifically voltage (0 to 10VDC), Current (3 - 100 A) and Temp (20 - 100C). I have the data acquisition module, and it works well. My task is to create preferably isolated signal gathering and conditioning units for each of the three channels.

    I decided to tackle current first. I have a variety of shunts but decided first to try one of the hall-effect modules that can measure DC. I bought two... A Tamura L08P100D15, and a Honeywell CSLA2CD. I started with the Tamura first. Data Sheet This has to be the worst data sheet I've ever seen. Anyway, the unit uses +/-15VDC, and despite my best efforts at hacking around a bit with a unipolar supply, I could not get it to work.

    I then tried the Honeywell (Datasheet, even less info!) And it worked fine, but the basic Vout is Vcc/2, meaning 4V with zero amps, and increasing linearly from there.

    What I'd really like is an output that starts at zero, not Vcc/2. The latter means I'd need a very accurate, stable voltage (8V) to power it, no drifting allowed. Any thoughts? How do I "shift" the output of the Honeywell, or can I make the Tamura work with a unipolar supply, as its output does start at zero. Thank you all!
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    395
    The blind leading the blind; for the Honeywell use an OP AMP as adder/ subtracter to eleminate 4V offset and adjust output.
     
  3. Chogy

    Thread Starter New Member

    Feb 25, 2009
    2
    0
    Thank you Bernard. I did a bit of experimenting with the Tamura, and without +/- 15V, it does not work. The Honeywell DOES work, and I found my data collection software will allow me to set 4.00V as the baseline... thus visually and functionally, it should work and display the data correctly. All I need now is a stable 8.00V, perhaps a reference will do given the low current requirement of the Honeywell sensor.
     
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