User manual

Figure 8-12: Vector Average of HX and HY Measurements
ACM Compass Calibration Step 3 – Adjust Parameters Manually
To correct for the biases and gains, determine offset and scale parameters that map the
measurements to the unit circle using the equation shown next.
1
22
=








−
+








−
S
O
S
O
Y
YHY
X
XHX
HX and HY are the raw measurements, X
O
and Y
O
are the offsets, and X
S
and Y
S
are the
scale factors. The expressions in the parentheses will be the corrected HX and HY values. These
four parameters can be adjusted by hand, iterating manually until the desired result is achieved, or
vector average the measurements by calculating the means of the HX and HY measurements
separately and using those components as the offsets. If vector averaging the measurements, use
the element of each component set with the largest magnitude after the offsets have been applied.
The scale factors are max(abs(HX
O
)) and max(abs(HY
O
)).
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