A diagram is a simple indicator of water. Most often used for alarm about the state of the water level in various designs. The sensor device is the "resistance" R3 scheme - is a conventional conductors.
Most often to maintain the reliability of the device as an electrode used silver or silver plate. Connection plate with wire to provide mechanical means (mounting hardware with a chrome finish). If the sensor is located at a considerable distance from the device (a few tens of meters), you must ensure the appropriate section of the wire and proper grounding of the device and water design. As a variant it is possible to make a sensor with two electrodes and to ground the design.
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