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  • #31
    The best way to approach this problem is one step at a time.

    1) Add ONE cable (without the scale attached) and check for issues.

    2) Remove that cable, then attach the other cable and check again. If either cable exhibits problems, swap it to the other axis input and retest.

    3) Add a scale to the one cable hooked up and retest.

    4) Remove that cable and scale and hook up the other set and retest. If either scale exhibits the problems, swap axis inputs and retest.

    Take notes so that you don't inadvertently test the same setup twice and make incorrect conclusions.

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    • #32
      Originally posted by SLK001 View Post
      The best way to approach this problem is one step at a time.

      1) Add ONE cable (without the scale attached) and check for issues.

      2) Remove that cable, then attach the other cable and check again. If either cable exhibits problems, swap it to the other axis input and retest.

      3) Add a scale to the one cable hooked up and retest.

      4) Remove that cable and scale and hook up the other set and retest. If either scale exhibits the problems, swap axis inputs and retest.

      Take notes so that you don't inadvertently test the same setup twice and make incorrect conclusions.
      Thanks I got hit with work so have to focus on that - i will do all you said and also take Jims advice and run a separate ground outside the main cables just in case their getting hit with anything weird to confuse them and report back with all my findings thanks
      Last edited by A.K. Boomer; 02-22-2021, 01:19 PM.

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      • #33
        Digital multimeter and scope for well under $100? OK, Flute makes a low end DMM which is good and under $100.

        But a digital scope for under $100? I just don't know about that. Even the $200+ and $300+ ones that I have seen are severely limited when searching for spikes. A digital chip will react to a spike that is far above that chip's maximum operating frequency so you need a scope that reliably captures spikes that are at least ten times the operating frequency of the chip in question. And that, in turn, means that the sampling rate of the digital scope would need to be AT LEAST several times higher than the 10X frequency I mentioned above. Since the digital scopes are made with digital chips, this is not often the case.

        And remember I am talking about the rated operating frequency of the chips, NOT the actual clock frequency that is used in your particular circuit.

        Frankly, if you are searching for those spikes, you are going to need a very, very good scope. And I would recommend an ANALOG scope, not a digital one.

        One way around this dilemma is the logic probe. A good logic probe can capture the fast spikes that the digital ICs are prone to. The only problem here is that a logic probe will react to the normal pulses in a digital circuit so they must be eliminated (turned off) first.



        Originally posted by PStechPaul View Post
        Have you tried removing and re-seating any ICs that are in sockets? I have sometimes found one that has a bent or broken pin that barely made contact and became intermittent.

        Without reasonable test equipment like a good DMM and scope, you are just "spit-balling", and from your remarks it's obvious that you are confused and frustrated. For well under $100 you should be able to get a decent DMM (Digital Multimeter) and DSO (Digital Storage Oscilloscope). I suspect that for some reason the pulses coming from the scales are noisy or distorted, which could be easily seen on a cheap scope. And the other possibility as previously mentioned is noise in the 5 VDC logic supply, which again can be examined with a scope.

        https://www.ebay.com/itm/Hantek-6022...z/222745314479 (from China)

        https://www.ebay.com/itm/FNIRSI-1C15...s/114618820016 (From China)

        https://www.ebay.com/itm/DSO112A-Dig...s/163977520096 (only 2 MHz but ships from KY)

        https://www.ebay.com/itm/Hantek-6022...S/283861178799 (20 MHz, ships from CA)

        https://www.ebay.com/itm/Oscilloscop...r/254694797287 (25 MHz ships from NJ)
        Paul A.
        SE Texas

        And if you look REAL close at an analog signal,
        You will find that it has discrete steps.

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