Single Electrode for water presence detection

Discussion in 'General Electronics Chat' started by rajesh.reddy, Oct 7, 2013.

  1. rajesh.reddy

    Thread Starter New Member

    Feb 6, 2012
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  2. WBahn

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    Mar 31, 2012
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    Look at the cable connecting the probe to the base unit. Do you see that it consists of TWO wires? What does that tell you about what is inside the probe?
     
  3. rajesh.reddy

    Thread Starter New Member

    Feb 6, 2012
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    But in the circuitry those two wires are joined together
     
  4. WBahn

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    Mar 31, 2012
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    How do you know this? I might be missing something, but I don't see anything in the information you linked to that indicates this.

    Don't hold out on us. If you have more information about the probe you want to have explained to you, then please share it with the folks you are asking for an explanation from.
     
  5. Sensacell

    Well-Known Member

    Jun 19, 2012
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    The sensor looks like it could be *more* than just an electrode, maybe it's more sophisticated than meets the eye?

    Maybe it's a mechanical impedance sensor, or some other more exotic technology?

    The typical electrical conductivity probe is not that great in murky-slimy-gunky real-world situations when you need real reliability.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    It's not an electrode - it's a current sensor. (per the mfg)
     
  7. WBahn

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    I finally found some information and, as wayneh indicates, it is a current sensor. In particular, it senses the current between the sensor and the earth-ground lead. The assumption is that the water is sufficiently conductive AND that there is a suitable ground path (such as the motor casing) to permit sufficient current to work. Probably good assumptions in most applications.
     
  8. wayneh

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    The source I found said the sensor senses MOTOR current, which drops when the sump pump is no longer loaded by water.
     
  9. MaxHeadRoom

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    Jul 18, 2013
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    Thats odd if the motor is an impeller type pump, which most sump pumps of that type are, The current tends to decrease with a restriction with either input or output blocked or partially blocked in an impeller type pump?
    Max.
     
  10. WBahn

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    Mar 31, 2012
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    How could the sensor mounted at a certain height sense motor current?

    According to the manufacturer's website, the single probe version (they also sell a two probe Hi/Lo model) turns on when the sensor detects current between the sensor and the grounded motor case. The control box (to which the motor is plugged in) senses the change in current that accompanies the loss of suction when the water falls below the pump's intake in order to know when to shut the pump off.
     
  11. wayneh

    Expert

    Sep 9, 2010
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    Oh nuts, you're right, I scanned the pdf too quickly and got it wrong. The probe IS a water (resistance to ground) sensor and it's the controller itself that watches current. So the probe turns the pump on when water touches it, reducing resistance to ground, and the controller shuts the pump off when it thinks suction is lost.
     
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