Test Rig Construction

Discussion in 'The Projects Forum' started by Steve1992, Feb 17, 2007.

  1. Steve1992

    Thread Starter Senior Member

    Apr 7, 2006
    100
    0
    Hi,

    Im building a test rig that can monitor waveforms from a pcb under test onto a CRO.
    Ive fiited a BNC socket to the test rig; so the user plugs a BNC-BNC coaxial cable to their
    CRO and the test rig.

    I want to know, do I need to use coaxial cable as well within the test rig: pcb (unit under test)
    test points to BNC socket on test rig?

    Or would multi-strand equipment wire be ok?
    The length inside the test rig needed would be approx. 300 mm.

    What do you do?


    I had a read the AAC 'Transmission Line' book, but I think that covers long distance cabling.



    Thanks.

    Steve
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    What is the nature of the signal you are monitoring with this test rig?

    Waveshape?, Frequency?, voltage swing?, Output impedance of the signal source being monitored?

    hgmjr
     
  3. Steve1992

    Thread Starter Senior Member

    Apr 7, 2006
    100
    0
    A video signal.

    I dont know using equipment wire over a short distance(pcb test point to BNC skt. on test rig) would affect its appearance.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    You indicate that the signal is video. You did not say so I imagine that you are dealing with baseband.

    Under the circumstances I think you should use the coax. In video it is generally the case that the video source impedance is 75 ohms and terminated by 75 ohms at the output end of the coax.

    hgmjr
     
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