Visually Inspecting logic signals on a logic analyzer

Discussion in 'General Electronics Chat' started by Billy Mayo, Apr 12, 2013.

  1. Billy Mayo

    Thread Starter New Member

    Mar 24, 2013
    Visually Inspecting logic signals on a logic analyzer
    This is what I have done
    a. The Pulse Width was correct for each logic signal and logic channel
    b. Time intervals apart from each pulse were correct and in sync with other logical signals
    c. Leading and Falling Edges were sharp and not rounded or slanted

    What other measurements can I do or what to look for?

    When troubleshooting Analog or Digital circuits, What frequency and waveform do you set the function generator at mostly?

    I set my up for sine waveform at 1Khz when injecting a function generator signal into a component to make sure its working right.

    Using a Square waveform at 1Khz is better for troubleshooting , because if the square waveform has rounded edges or is slanted top or bottom , leading edge and falling edges are skewed , than it's a bad capacitor

    What do you use a square waveform on the function generator for when troubleshooting using a square waveform?
  2. WBahn


    Mar 31, 2012
    I use whatever frequency is appropriate for the circuit being tested and the test I am performing. For some circuits 1kHz is way too fast and for others it is way too slow.

    If you aren't seeing any slant or rounding of the signal edges it just means that you aren't zoomed in enough. All signals (well, inductive kicks are as close to an exception as you are likely to get) take finite time to transition and make something other than right-angle transitions. In fact, you WANT them to, otherwise you have energy in very high harmonics. How much slew rate and distortion is acceptable and what it indicates depends on the time scale involved and the particulars of the circuit.
    Last edited: Apr 12, 2013
  3. MrChips


    Oct 2, 2009
    You are attempting to create a generalize rule where none exists nor is applicable.

    I agree with WBahn. Every situation is different and you have to set up the function generator and scope to suit the situation.

    The slew on rising and falling edges has many more dependencies and has almost nothing to do with a bad capacitor.
    Last edited: Apr 12, 2013