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TMAG5273: Magnetic field values

Neha Kawadkar
Prodigy 20 points
Part Number: TMAG5273

Tool/software:

I am using SparkFun Linear 3D Hall-Effect Sensor - TMAG5273 in my application to detect magnetic field of relay. I have a relay with 55A, 480VAC rating. I am trying to capture the magnetic field of the relay by using Arduino Uno with #include "SparkFun_TMAG5273_Arduino_Library.h" Library used.  I have done the configuration of the TMAG5273 sensor as required. As per the datasheet the range should be between -40 to +40 but I am getting values in between only -2.0 to 2.0mT while the range configured +-40mT. Are these values looks good and expected as per relay rating? Why these values not going up +-40mT? Is there any configuration to increase sensitivity output values, I see in datasheet there is two registers "MAG_OFFSET_CONFIG_1" and "MAG_OFFSET_CONFIG_2" how to use these registers?

  • 0
    TI__Mastermind 20980 points

    Neha,

    This may all depend on positioning of the sensor.  In the case that you are attempting to measure the current through the closed circuit path in the relay, the field expected at any distance could be calculated using the equation

    B = μ0 * I / (2 * π * r) 

    If you are measuring 2mT with a current of 55A, then the expected distance from the conductor is about 5.5mm. To measure 40mT with 55A of current, it would be necessary to place the sensor about 275um from the wire.  The fact that you measured 2mT seems fairly reasonable to me in this case.

    If measuring the field from a coil used to drive the relay, then this is a bit more complicated and requires you to know the number of turns and the radius of the coils.  The equation here is:

    B =   μ0 * N * α2 * I / (2 *(α2+ r2)(2/3) )

    Where:

    N is the number of turns

    α is the radius of the coil

    and r is the distance from the center of the coil

    Thanks,

    Scott

  • 0 in reply to Scott Bryson
    Prodigy 20 points

    Thanks Scott. It is helpful.