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Rotational sensor axial and tangential movement insensitivity

Christos Karatzoglou
Intellectual 405 points

Hello,

In a previous post

Angle position axis movement insensitive - Sensors forum - Sensors - TI E2E support forums

e2e.ti.com
Hello, I am trying to build an inductive angle position measurement system using a target somehow different from what you have in application notes. The idea

I"ve described my rotational sensor to measure angle.  I"ve now changed the target and have another coil next to the one that measures the contour for rotation to compensate z axis movement, and works just fine. There is although a small movement along x and y axis too. This movement isn't big enough but creates some error to the final angle measurement. What would be the best approach for coil-target design to minimize as possible the error from x and y axis movements. I should say that there is no space available for more coils on the PCB. 

  • 0
    TI__Genius 14270 points

    Hello Christos,

    I understand that any additional sensors are not possible, but can you consider using a rectangular or oval shaped sensor instead of a circular or rectangular sensor? The longer dimension of the sensor will have a nearly uniform field for a portion of the longer edge. In that way, lateral motion along the longer edge will produce the same response. In this way, you can reduce the sensitivity in one axis.

    Regards,

    ChrisO

  • 0 in reply to Chris Oberhauser66
    Intellectual 405 points

    Hello Chris,

    I've already used a rectangular coil which is bigger in the direction of x axis but the coil is still rather sensitive. I'll try to make it bigger.  Could working frequency play any particular role on this kind of sensitivity?

    Regards

    Christos

  • 0 in reply to Christos Karatzoglou
    TI__Genius 14270 points

    Hello Christos,

    If your target is 3+ skin depths thick, then no, changing the working frequency will not have a significant effect.

    Regards,

    ChrisO

  • 0 in reply to Chris Oberhauser66
    Intellectual 405 points

    Hi Chris,

    Thanks once again for the quick feedback. As a last question I was wondering if I could increase the number of turns of my coil would this result in more insensitivity along x and y axis?. By the way something strange happens during x axis movement. So when the target is in the middle of the coil a have the smallest frequency and as I move left or right the frequency is increasing. I was supposed to have the opposite effect wasn't I? I mean maximum frequency (less inductance) in the center of the coil and less frequency (more inductance) as I move left and right.

    Regards

    Christos