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TMAG5273: "Sensitivity Drift from from 25C, X, Y, Z axis" query

Oliver Vogel-Reed
Prodigy 10 points
Part Number: TMAG5273
Other Parts Discussed in Thread: TMAG5170

Hello,

I am looking to calibrate these sensor IC's to within a known uncertainty. I understand there will be a drift in offset and sensitivity as the temperate deviates from 25C. These drift values are given in section 6.7 and 6.8. The offset drift is stated in uT/°C, and unless I am misunderstanding I was expecting the sensitivity drift to be given in %/°C but it is given as ±5.0%.

Does this mean that the maximum change in sensitivity as the chip approaches its maximum operating temperature (125C) is ±5.0%? Therefore the value is ±0.05%/°C?
Or is there another way I am meant to use this value when evaluating equation 20 (section 8.1.5 pg39)?

Many thanks,

Oliver

  • 0
    TI__Expert 7495 points

    Hi Oliver,

    Sensitivity drift is often expressed as ppm per degree or as a total %.  Since the TMAG5273 datasheet expresses it as a total %, you should put a value of 0.05 for the SENSDR parameter in the equation. 

    Regards,

    Mekre

  • 0 in reply to Mekre Mesganaw
    Prodigy 10 points

    Hi,

    That makes sense, but I guess I'm still confused at how to achieve precision measurements given that 5% parameter. If I calibrate at 25C then take measurements at 26C, I have to apply a 5% uncertainty? Or perhaps is there a broader definition for what 'room temperature' is, say 25C +/- 3C.

    I'm aware that in reality the change in reading will be very small. But my work requires that I precisely quantify the uncertainty in the measurements I take, so sorry if this line of inquiry is a bit tiresome. That need for quantifiable uncertainty though does mean that if the datasheet states a drift of 5% and no range for 'room temperature' then on paper I cannot achieve a precision greater than 5%?

    Thanks,
    Oliver

  • 0 in reply to Oliver Vogel-Reed
    TI__Expert 7495 points

    Hi Oliver,

    I will check internally if we have any additional data that we could provide.  Can you tell me what application is this for?

    Also, if high-precision is a key requirement for this system, I would recommend the TMAG5170  device here.

    Regards,

    Mekre 

  • 0 in reply to Mekre Mesganaw
    Prodigy 10 points

    The application uses between 2 and 4 of these chips for measuring magnetic field gradients inside tight spaces in medical testing devices (in 3 axes). The issue is that any calibration or sensing equipment that we make in house must have a NIST traceable calibration (which we will perform ourselves) which includes stating a quantifiable uncertainty.  

    While high precision is desirable it is not an explicit requirement, the requirement is quantifiable precision. 

    Thanks,
    Oliver

  • 0 in reply to Oliver Vogel-Reed
    TI__Expert 7495 points

    Hi Oliver,

    Unfortunately, I was not able to find any additional information that we could provide on the sensitivity drift.  If you want less uncertainty in these measurements, I would recommend the TMAG5170 since it has tighter temperature specs.

    Regards,

    Mekre