I'm curious about the disconnecting of the flowmeters in the quote above. Did you do this at the PLC terminals, or did you do it out in the field so that there was still wiring and possibly conduit still connected to the PLC.
Wires were still on PLC going to terminal blocks.
Random HSC pulses from non-connected devices are removed whrn pull-up resistor is installed.
I have a clue... I have two 24VDC power supplies. One powers high-current DC pumps at 24VDC, the other powers all the instrument loops, including the flowmeters. If I take a voltage measurement from panel ground to 24v+ on my pump supply, my meter is solid at 24V... If I do the same thing to my I/O supply, voltage starts at 24 and quickly falls. Sometimes, I only measure 8v...
Now, it gets trickier... all my I/O is working, except for these flowmeters. The 24v supply in question outputs 24v measured direct off the supply using 24v +/- terminals, so this panel ground... gets me thinking. I switched supplies just in case, same effect. Any electrical whizes have any ideas on this one? I am not over-drawing current.
Where is my panel grounded to? Not earth, at least not nearby. It is grounded to a breaker panel located about 100' away through conduit of course.
Please remember, these meters worked flawlessly for 8 months...
I am almost positive (no pun intended) that it is an electrical issue. I have a new flow sensor cable coming tomorrow. This will QA my sensor question. I;'m expecting a new meter will not work.
Thanks All for staying tuned!