Phoebe guidesTry this in the MPU6050 motion-offset lab, where you change the X acceleration and see the corrected reading and motion state.
1. Start with two rulers
The IMU ruler measures acceleration in counts. The barometer ruler measures a height change through pressure. Neither raw number is yet a trustworthy event.
2. Map gravity to counts
At the chapter's +/-2 g setting, a still upright Z axis should be near 16,384 counts. A 0.1 g motion threshold is therefore about 1,638 counts away from the 1 g reference.
3. Map height to pressure
For small changes near sea level, a 3 m floor gives 36 Pa, or 0.36 hPa. Compare that result with the stated +/-0.12 hPa relative accuracy before calling a floor.
4. Keep drift separate
A constant gyro offset accumulates with time. A pressure scale check cannot repair it; the IMU needs a still reference or another long-term orientation source.
5. Decide what passes
First verify the still count and sign. Then verify the pressure step against a known height. Finally record the range, offsets, time, weather, and mounting state that make those checks repeatable.
6. Check yourself
Why is 0.1 g about 1,638 counts?
Why is a 3 m floor about 0.36 hPa?
Does a 3.0 ratio prove the floor every time?
The count conversion fixes the acceleration scale, while the height comparison uses a constant near-sea-level pressure gradient and the stated relative-accuracy figure. Weather, airflow, filtering, mounting, and reference drift are not resolved by that comparison, and a pressure check does not correct gyroscope drift.
- 16,384 counts/g
- Configured acceleration-to-count scale
- 0.1 g
- Motion detection threshold above gravity reference
- 12 Pa/m
- Approximate pressure change per metre of height
- +/-0.12 hPa
- Stated barometer relative pressure accuracy
- 0.01 deg/s
- Example gyroscope zero-rate bias
They support a calibration runway, not a complete MPU6050 or BMP280 error model and not a guarantee of floor detection.