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Inductive sensors

Discussion in 'General Electronics' started by Roger Isaksson, Aug 16, 2004.

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  1. Hi, we are in the process of improving our inductive sensors, or
    possibly replace them with other types of sensors. The absolute
    precision is not decisive with our differential technology. What is
    important is the capability to detect (edge detect) passing cog teeth.
    Typically these edges are measured on an underwater submerged spinning
    cogwheel. A passing cog induces an electromotive force, due to the
    difference in the magnetic field surrounding the coil as the cog
    passes, this results in a voltage that is measured. The rate of
    passing teeth are below 20/s. The required presicion of the detected
    cog edge should be about about 2.5ms and the measuring distance should
    be about 8-10mm(preferrably more). The cog height, measured from the
    cog wheel axis, is larger than 200mm. The sensor is measuring
    submerged in water and the cog wheel are made of metal. The sensor
    will be mounted threaded into the cog wheel housing. The housing are
    made of magnetic steel, which decreases the sensing distance, using
    inductive sensors. The sensor is mounted perpendicular to the cog
    wheel axis. The diameter of the sensor housing is 25mm.

    Does anyone have any ideas? Right now we can detect up to 8-10mm with
    our prototype inductive sensors. The sensor has a 10x60mm cylinder
    neodyne magnet, surrounded by a coil(0.15mm wire) with aprox 4000revs.
    There are a few parameters that could be altered:

    # The diamater ratio between magnet and coil.
    # The geometric shape of coil and magnet, edges, konicity, etc.
    # Choise of magnet, parameters such as field strength and field
    # Number of revs in the coil and wire diameter.


    Roger Isaksson
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