Flow Sensor wire

Discussion in 'Professional Discussions' started by ArTurf, Aug 17, 2019.

  1. ArTurf

    ArTurf LawnSite Fanatic
    Male, from Ark
    Messages: 6,235

    I've installed a handful of flow sensors with regular multi-strand, no problems

    I notice there are specific wire cable for sensors, any reason to use this "special" wire?
     
  2. jdmccay

    jdmccay LawnSite Member
    Messages: 18

    I'm pretty sure the special wire is for a flow meter or flow transmitter, which actually transmits flow data back to the clock, so it requires wire that can transmit data. Whereas the ones with regular wire are for flow sensors and pressure switches, which can only tell if there is or isn't flow, not data about psi and fps.

    Grain of salt; that's only my rudimentary understanding of it, someone might have a better answer.
     
    Ron Wolfarth likes this.
  3. benhargreaves

    benhargreaves LawnSite Member
    Messages: 113

    The special wire I'm aware of is shielded wire. It's used to prevent interference. Beyond that, I'm a bit out of my depth.

    From what I understand of pulse meters, they send a low current pulse for each unit of water that flows through it. So any stray current could be enough to create incorrect readings. The electric field around an active zone wire could potentially create enough of a current in the sensor wire to cause interference and bad readings. Hence, the spec for shielded wire.
     
  4. Michael - Toronto

    Michael - Toronto LawnSite Member
    Messages: 22

    I concur with Ben's comment above.

    Recently, I had to install 300 feet of cable connecting a Hunter flowmeter to the Hunter controller. Because of site constraints, I had no choice but to install the cable in the same trench as a cable controlling the master valve and several other zone valves. For 30 feet under a roadway, the cables shared the same 1 inch conduit.

    I used a special shielded cable for the flowmeter cable, and made sure the shield was grounded at both ends. It has worked flawlessly.

    The special cable cost more, but it would have cost me a heck of a lot more if I had used regular cable for the flowmeter and it didn't work reliably due to interference.

    Michael
     
  5. RhettMan

    RhettMan LawnSite Silver Member
    from Texas
    Messages: 2,945

    accidentally hit the post button.
     
  6. OP
    OP
    ArTurf

    ArTurf LawnSite Fanatic
    Male, from Ark
    Messages: 6,235

    Glad to see they released you
     
  7. Delmarva Keith

    Delmarva Keith LawnSite Senior Member
    Messages: 739

    I’d use a shielded twisted pair. My understanding is that the typical voltage induced in a conductor by various surrounding EMF gets cancelled in twisted pair because the magnetic field lines of the EMF noise through one “twist” of twisted pair is exactly opposite to the next “twist” and so on down the wire. The induced magnetic field noise tends to cancel itself. Maxwell’s equations, so on, and on . . . . The shield will filter rf noise.

    If it’s far away from any magnetic fields (including house or service entrance wiring) and no huge rf sources, any wire is likely fine, but why take chances. The callback you save may be your own. :)
     
  8. Delmarva Keith

    Delmarva Keith LawnSite Senior Member
    Messages: 739

    If I could make a humble recommendation, next time maybe only ground one end of the shield (I’d suggest the controller end). If both ends are “grounded,” any difference in potential in the grounds at each end (which is more or less inevitable over long distances) will cause current flow in the shield and current flow in a wire creates a magnetic field and any change in a magnetic field induces voltages in the conductors the magnetic field pass across (Faraday’s law) and . . . can cause interference.

    It’s called ground loop. In most places you can get a perfect 60 Hz signal from the conductors shielded by a ground looped shield, from the electricity transmission infrastructure all around. If the controller input impedance is high enough, it will not get accurate data from the sensor.

    If that’s TMI, it’s a slow day here and I’m just spouting off . . . :)
     
    Sprinkus likes this.
  9. RhettMan

    RhettMan LawnSite Silver Member
    from Texas
    Messages: 2,945

    ...I jumped the fence :)

    Perhaps unsolicited and uninteresting, but:
    Have you ever tried a rachio gen 3 and rachio wireless flow meter pair? Its got its limitations for certain, but it certainly is neat in the right application Just a somewhat related sidenote that is somewhat unrelated.

    (Otherwise glad you asked this question i wasnt aware of interference sheilding wire insulation.)
     
  10. OP
    OP
    ArTurf

    ArTurf LawnSite Fanatic
    Male, from Ark
    Messages: 6,235

    Never tried Rachio but I've noticed you kinda have a crush on them. My son-in-law installed one at their house and I sorta looked at the app. The hardware really turned me off though, maybe they've improved it?

    Tell my what you like about it
     

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