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TMAG5273: ADC gain

Giovanni de Sanctis
Prodigy 80 points
Part Number: TMAG5273

Hello 


I read in the specs for the TMAG5273 that the ADC gain can vary by up to +/-20% (sensitivity error). Should I assume that this figure is independent even between axes within the same device, or are the errors from the 3 axes somehow related? In other words, since the angle is essentially a ratiometric measurement, I could live with both X and Y axes having +20% the specified sensitivity, as their ratio would be unaffected. Vice versa if the errors from X and Y axes can swing independently, then their ratio's error will be roughly even twice as much.

I am asking because I have the system calibration stored separately from the board hosting the TMAG. Since the final user will be allowed to fit different TMAG boards, I would like to know if I need to calibrate the TMAG locally (ADC sensitivity for each channel, the offset is already calibrated and stored locally in the absence of field), or if the overall system calibration will suffice.

I have very strict accuracy specifications (+/-1 degree max error).

Many thanks

Giovanni

  • +1
    TI__Mastermind 23045 points

    Hello Giovanni,

    Thanks for posting to the sensors forum. That is partially correct, the sensitivity error can drift up to 20% but keep in mind that we also spec the sensitivity mismatch between different axes. So even though there can be a sensitivity difference between the sensors we aim to reduce the this value to keep the sensor angle measurement errors as low as possible.

    For the most part having a system calibration should help reduce most of the errors you expect to see, but if a sensor level calibration is possible I would recommend doing this. My concern are differences between sensors themselves so calibration would reduce any possible errors introduced by a slight variance in a device. My main concern is installation of a new TMAG board, error in installation or if the tolerances on the mechanicals are off then this could contribute to some error.

    Best,

    Isaac

  • 0
    Prodigy 80 points

    Hello Isaac

    Thank you very much for your prompt reply. I had completely missed the specs on sensitivity mismatch between axes, and a 0.5% error is a lot more reassuring :-) As you say, it makes sense that you try to keep that to a minimum to guarantee angle accuracy.

    You also have a good point regarding mechanical tolerances on the TMAG board. I guess we will have to wait for the design finalized and prototyped to determine that.

    Thanks again

    Giovanni