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Best possible solution to measure magnetic flux densities in the ranges of 0-200 Guass.

Other Parts Discussed in Thread: DRV5056, DRV5055

Dear sir,

We are working on gear box health monitoring project. And wanted to sense changes in magnetic flux densities due to gear tooth interaction with magnetic field. (gears are made up of ferromagnetic material like mild steel).


Basic idea is, we need a sensor which will sense the changes in magnetic field whenever tooth pass by. We are thinking to place magnet near one side of tooth and other side will place sensor. So whenever tooth pass by it will have some effect on magnetic flux densities. and by sensing those changes we can track health condition for each tooths.


We calculated the changes in field strenghts by using laboratory gauss meters.For our particular configuration We found that the field strenghts varies between 65-125 guass.


Now we need a magnetic field sensor with sensing range nearby above mentioned range. so that we can include it in our project.


Kindly suggest us best suitable sensor for our application. As this is R & D project we can do modifications so suggest if you have any ideas.


Thank you
Mandar kothavade

  • Hello Mandar,

    Thank you for using the TI forum. It looks like DRV5056 will be good for your application. Specifically, the A1 gain version should be a good fit for you sensing range. Be sure to check the other device specifications, including bandwidth, to ensure that the DRV5056 will meet all of your requirements. Also, note that you will need a bypass capacitor near the sensing device.
  • Thank you Mitch M for your quick reply. 

    I was checking the datasheet of DRV5056. But found they have mensioned its full-scale magnetic range as (+-) 19mT as minimum range. Now I am little confused about this, is it the minimum value of magnetic field above which this sensor can sense the magnetic fields? Or range of sensor is -19mT to +19mT. 

    If its minimum value of magnetic field which sensor can sense then This sensor is of no use to me because I my minimum field strength  to sense is 65G=6.5mT.  If its other case then This sensor will work in my application. 

    Again I want to sample the data at high speeds like more than 10KHz. And the sensors datasheet says its sensing bandwidth is 20KHz. So I think it will suit my application.

    Again what is resolution of this sensor?  I mean to say what is smallest value of change in magnetic field this sensor can detect?

    Kindly confirm these parameters. And help me to understand its exact meaning of them.

    Again thank you for helping me.

    Thanks & Regards 

    Mandar B. Kothavade

  • Hello Mandar,

    The DRV5056 is unipolar so the full-scale range is just +19mT at 3.3V and + 20 at 5V (for the A1 version), as shown in the image below.

    If you need bidirectional (±21mT, then you can use the DRV5055), but from what I understand of your setup the unidirectional DRV5056 is the better choice.

    Since it is unidirectional, the DRV5056 senses from 0mT to 20mT (or 19mT at 3.3V), as in the picture below:

    The smallest change in magnetic field that the sensor can detect largely depends on the noise of the system.  The Output-referred noise for the DRV5056 is:

    In general the resolution will approximately be: (max ∆mT)/((VOUTmax - VOUTmin)/noise)

    Note, VOUTmax = VL= Vcc - 0.2V, and VOUTmin = 0.6V

    So, with a 5v system, the mT resolution for the A1 would be approximately:

    20/((4.8-0.6)/0.024)=0.114286mT

    And with a 3.3v system, the mT resolution for the A1 would be approximately: 

    19/((3.1-0.6)/0.024)=0.1824mT

    If more noise is introduced to the system then this resolution will go down.  Also, the quality of the ADC may also lower resolution.

    Let me know if you have any more questions.