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DRV425: Definition of Linearity Error

user5262213
Prodigy 20 points
Part Number: DRV425

I'm working with the DRV425 for magnetic field sensing. At the moment I'm not shure about the Linearity Error mentioned in the DRV425 Datasheet. There is one for the Flux-Gate itself and one for the Shunt-Sense Amplifier. Both are mentioned there in percent/ppm. Do these mean an relative error to the value currently sensed or an error related to the Full-Scale value of the sensor? 

Thanks for your help

Felix

  • 0
    TI__Mastermind 26485 points

    Hi Felix,

    Thank you for using the E2E and choosing TI.  The error is using the full-scale value.  Another way to look at it is after you remove the gain and offset error and come up with a line that represents the transfer function or best fit line on the transfer curve.  Then you calculate the error can be 0.1% error from the value you expect from the best fit line.

    So once you get a best fit line the error from that expected line is 0.1% for the Fluxgate and 12ppm for the difference amplifier.  Since the error is so much lower on the flux-gate I will give an example for the system combined and only use the flux-gate values.

    If we use a Rshunt of 100Ω we get a gain of 4880 V/T which give a full scale Vout  at 0.491mT.  You can use the DRV425 System Parameter Calculator for this.

    So if we measure a signal of 0.1mT we would expect an output of 0.488V.  The error due to linearity would be 0.488V±0.488V*0.001 = 0.488V±488uV. 

    Hope this helps,

  • 0 in reply to Javier Contreras4
    Prodigy 20 points

    Hi Javier,

    thanks for your fast reply. Maybe I am wrong with the terms, but the thing you describe is an error related to the actual measured value, which is not an error related to the full-scale-value, isn't it?

    So related to your example, the output value of the flux-gate would be V_out+-(V_out*0.1%) and not V_out+-(V_max*0.1%). In this example V_max is the maximum output voltage of the sensor (full scale) and only the nonlinearity error is observed. Maybe you can give me a hint, if I am right.

    Many Thanks!

    Felix

  • 0 in reply to user5262213
    TI__Mastermind 26485 points

    Felix,

    The linearity error will be based on the output but please keep in mind that this measurement error is after gain error and offset error are calibrated out.  When using the DRV425 to measure magnetic fields you will most likely hit other errors in the system that will most likely be much larger than this.  I would assume this will be you least significant error.

    For example if you are going to measure a magnetic field from a magnet the placement of the magnet will drift and placement relative to the part is important.  The placement of the sensor inside the package has a tolerance of 0.025mm in the X,Y, and Z directions.

    Please let me know if you have other questions regarding your application.