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DRV5053: Increasing Hall Effect Sensitivity of DRV5053

Satish Veda
Prodigy 140 points
Part Number: DRV5053

Can one increase the sensitivity by using '2' Hall-Effect sensors (DRV5053) back to back (opposing slopes of mV/mT), with '1' magnet on one side of these sensors?

I thought that Hall the Hall Voltage: Vh = Rh[I/T * B)

and hence he Hall Voltage is Inversely proportional to the thickness of the hall element. Also directly proportional to the incident Magnetic Flux density (B).

It is my understanding that the Magnetic Flux density will be reduced (by a value equal to F = qvB.

Where the Force 'F' results in a hall voltage Vh.

This Force is halved due to the fact that  '2' sensors are used back to back (for a given, common magnetic field).

CAN ANYONE VERIFY the above statements?

Regards,

-Satish

  • 0
    TI__Expert 5705 points

    Hi Satish,

    Please see my responses below in red.

    Can one increase the sensitivity by using '2' Hall-Effect sensors (DRV5053) back to back (opposing slopes of mV/mT), with '1' magnet on one side of these sensors?

    Yes. The example below shows that the differential output of two sensors with opposing slopes would give you twice the gain as the individual sensors over the same input range.


    I thought that Hall the Hall Voltage: Vh = Rh[I/T * B) and hence he Hall Voltage is Inversely proportional to the thickness of the hall element. Also directly proportional to the incident Magnetic Flux density (B).

    Correct. The exact equation for the Hall voltage is documented here

    It is my understanding that the Magnetic Flux density will be reduced (by a value equal to F = qvB.Where the Force 'F' results in a hall voltage Vh.This Force is halved due to the fact that  '2' sensors are used back to back (for a given, common magnetic field).

    Not true.The flux density at a point is independent of the number of sensors measuring it. Both sensors will experience the same force and produce output voltages determined by their respective transfer functions.

    Best Regards,

    Harsha


  • 0 in reply to Harsha Munikoti
    Prodigy 140 points
    Vh = Rh (I/t) * B
    Where Rh is the Hall Effect Co-efficient
    I is the current flow thro' the sensor in amps
    't' is the thickness of the sensor in mm
    B is the Magnetic Flux Density in Tesla's

    Question 1:- How can the Vh (Hall O/P voltage) be the same for twice the sensor thickness (with the same 'B')??
    Since the thickness equates to "2 * t" ?
    Question 2:- How can the Magnetic Flux be the same, through '2' sensors, w/o any attenuation due to 2x the permeability?
    TIA
    -Satish
  • 0 in reply to Satish Veda
    TI__Expert 5705 points
    Satish,

    Q1. Each sensor has its own internal current source (I) to bias the hall element. If the hall elements have the same dimensions and Rh then for the same incident field and bias current, each hall element will individually develop a voltage |Vh| (and not 1/2 x |Vh| as your post implies).

    Q2. To my knowledge hall elements are made of non-magnetic metals as they do not get magnetized in the presence of strong magnetic fields. Non-magnetic implies low magnetic permeability. Therefore the applied flux density remains unaltered in the space around each element and they experience the same |B| if they're at the same location.

    Best Regards,
    Harsha
  • 0 in reply to Harsha Munikoti
    Prodigy 140 points

    >>Non-magnetic implies low magnetic permeability.

    That's precisely my point!

    B = mu * H

    So with TWO sensor's permeability it halved (it definitely cannot be the same as ONE hall sensor).

    So each Hall sensor will see half of the 'B' (flux density), when '2' are used back to back.

    So since Vh is directly proportional to 'B'. The transfer function (mT--->mV) cannot be the same as using '1' Sensor.

    Can you verify this with your resident physicist.

    TIA

    -Satish

  • 0 in reply to Satish Veda
    TI__Expert 5705 points
    I don't know any resident physicists at TI but the fact is that the B-H transfer characteristic of a material (i.e. its magnetic permeability) is fixed in any volume of the material. In other words, you cannot change the magnetic permeability of the Hall element by simply increasing its size.

    Best Regards,
    Harsha
  • 0 in reply to Harsha Munikoti
    Prodigy 140 points
    Below is what I obtained from Wiki......
    "In general, permeability is not a constant, as it can vary with the position in the medium, the frequency of the field applied, humidity, temperature, and other parameters."


    I think I have the answer. Thank you.