This library provides a calibration class which you can use to dynamically calibrate your MMA7361.
It's not recommended (or required) that you calibrate your device every time; you can instead take measurements from one calibration session and use them statically with your device thereafter.
While calibration is running, you should carefully rotate the sensor through all sides, spending some time on each side to "wobble" the sensor and find its absolute zero point.
The calibrator measures the "stability" of the readings, in the hope to only capture values which represent stable 1g readings (gravity) rather than any acceleration or shock induced by operator handling.
The example calibrator also shows the "raw" extreme values, so if you over-G or under-G the accelerometer, you will know.
The calibrator uses a stack of averages to locate the extreme sensor values for the sensor at 1g.
In testing, minimum values were between 230-250, with maximum values between 710-780.
Note the values from the Serial output under the CALIBRATED heading:
Rate: 1704
X=469, Y=463, Z=729
CALIBRATED
X: min=250 max=703
Y: min=284 max=785
Z: min=217 max=706
EXTREMES
X: min=228 max=740
Y: min=157 max=801
Z: min=174 max=880
VECTOR: X=-0.03, Y=-0.28, Z=1.10, G=1.13
These values can be used to configure the MMA7361Calibration struct with static calibration figures:
calibration.xMin = 250;
calibration.xMax = 703;
calibration.yMin = 284;
calibration.yMax = 785;
calibration.zMin = 217;
calibration.zMax = 706;
See the code under static-calibration as an example of how to use static calibration.
These examples are intended to be used with the following environment
- Teensy 3.1 (Arduino derivative)
platformio initplatformio run --target upload