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DRV5056-Q1: Shaft Position Detection - Effect of Material on Magnetic Field

Andrew Pratchett
Prodigy 10 points
Part Number: DRV5056-Q1

Hi,

I'm developing a position detection system to control the position of a shaft as it slides past the hall sensor (see my picture below).

Due to space constraints, the magnet is fitted to the shaft.

The air gap between the magnet and the sensor is 1mm at the moment, although i can probably increase it if necessary.

The shaft has to be made from hardened steel, which is of course magnetic! Please could someone advise what effect will this have on the ability of the DRV5056-Q1 to sense the position of the magnet?

Thanks in advance.

Andrew

  • +1
    TI__Genius 16620 points

    Andrew,

    Welcome to E2E, and thanks for reaching out!  You are absolutely correct that the steel will influence the magnetic field.  With your drawing as a reference, the N pole is attached to the sheet metal.  Since the steel is able to become magnetized, the return path for the magnetic field will concentrate more readily as it exits from N and returns to S.  

    Effectively what this will do is draw more of the field on the side of the magnet where the steel is, and will likely reduce the overall field strength on the opposite side that is facing the sensor at the sensor location.  However, we can still look at the field lines somewhat as if they are a closed electrical circuit.  What exits from N, must return to S.  At 1 mm, the magnetic flux density will still very likely be quite significant.   

    Thanks,

    Scott

  • +1
    Prodigy 10 points

    Hi Scott,

    That confirms my suspicion as to how the field/sensor will behave.

    Many Thanks

    Andrew