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Signet pH/flow probes and S3L

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  • Signet pH/flow probes and S3L

    Has anyone figured out how to talk to Signet S3L sensors over RS232? According to their manuals, it's a serial ASCII format, so I'd imagine a PLC would be able to communicate if it had the right strings to request data...

  • #2
    I have not tried to talk to anything from Signet.
    The Do-more has successfully talked to all the ASCII devices that I have tried so far.
    Circumstances don't determine who we are, they only reveal it.
    Jason Wolthuis


    • #3
      Yeah, I definitely wasn't concerned about any limitation of the Do-More, of course! Just interested in hearing from people out there.


      • #4
        Sorry to revive an old thread but did you ever make any progress communicating with the Signet devices via S3L?


        • #5
          I hadn't had the time, but I'm planning on working on it tonight. I'll post my results.


          • #6
            Let me know how it goes.

            I just noticed this product on the GFPS website, if we can't get these sensors talking directly to a PLC this may work.


            • #7
              ...and I'm the worst. I worked so late I completely forgot about it. I'm going to start this now.


              • #8
                Okay, a few days late, but here's what I found:

                The S3L protocol is TTL-level single-wire bus. The sensors are powered by 5VDC, and the data line is referenced to ground. It communicates at 9600 bps, with 7 data bits, no parity, 1 stop bit, and no flow control.

                I'm able to snoop on the traffic between a Signet display using an Arduino as a TTL converter. I've identified a few things about the data stream, and can reliably pull data from it into a Do-More simulator (even scaling to an analog output), but any attempt to talk back to the sensor fails. Additionally, the sensor doesn't send any data without a request from the display (which I don't seem able to replicate).

                I'm too far in to stop now. I'll keep you posted.


                • #9
                  Sorry everyone. I got bogged down with a bunch of projects. I'll get back to working on this in a couple of weeks.