The TMAG5273 offers independent configurations to perform linear position
measurements in X, Y, and Z axes. To calculate the expected error during linear measurement,
the contributions from each of the individual error sources must be understood. The relevant
error sources include sensitivity error, offset, noise, cross axis sensitivity, hysteresis,
nonlinearity, drift across temperature, drift across life time, and so forth. For a 3-axis
Hall solution like the TMAG5273, the cross-axis sensitivity and hysteresis
error sources are insignificant. Use Equation 19 to estimate the linear
measurement error calculation at room temperature.
Equation 19.
where
- ErrorLM_25C is
total error in % during linear measurement at
25°C.
- B is input magnetic
field.
- SENSER is sensitivity error in decimal number at 25°C. As an example, enter
0.05 for sensitivity error of 5%.
- Boff is offset error at 25°C.
- NRMS_25 is RMS
noise at 25°C.
In
many applications, system level calibration at room temperature can nullify the offset and
sensitivity errors at 25°C. The noise errors can be reduced by internally averaging by up to
32x on the device in addition to the averaging that could be done in the microcontroller.
Use Equation 20 to
estimate the linear measurement error across temperature after calibration at room
temperature.
Equation 20.
where
- ErrorLM_Temp is total error in %
during linear measurement across temperature after
room temperature calibration.
- B is input magnetic field.
- SENSDR is sensitivity drift in decimal number from value at 25°C. As an
example, enter 0.05 for sensitivity drift of 5%.
- Boff_DR is offset drift from value at
25°C.
- NRMS_Temp is RMS noise across temperature.
If
room temperature calibration is not performed, sensitivity and offset errors at room
temperature must also account for total error calculation across temperature (see Equation 21).
Equation 21.
where
- ErrorLM_Temp_NCal is total error in %
during linear measurement across temperature
without room temperature calibration.
Note: In this section, error sources such as system mechanical vibration, magnet temperature
gradient, earth magnetic field, nonlinearity, lifetime drift, and so forth, are not
considered. The user must take these additional error sources into account while calculating
overall system error budgets.