UM001
81
6.2
IMU Configuration Registers
6.2.1
Magnetometer Compensation
Magnetometer Compensation
Register ID : 23
Access: Read / Write
Comment : Allows the magnetometer to be compensated for hard/soft iron effects.
Size (Bytes): 48
Example Command: $VNRRG,23,1,0,0,0,1,0,0,0,1,0,0,0*73
Offset Name
Format
Unit
Description
0
C[0,0]
float
-
4
C[0,1]
float
-
8
C[0,2]
float
-
12
C[1,0]
float
-
16
C[1,1]
float
-
20
C[1,2]
float
-
24
C[2,0]
float
-
28
C[2,1]
float
-
32
C[2,2]
float
-
36
B[0]
float
Gauss
40
B[1]
float
Gauss
44
B[2]
float
Gauss
This register contains twelve values representing the hard and soft iron compensation parameters. The
magnetic measurements are compensated for both hard and soft iron using the following model. Under
normal circumstances this register can be left in its factory default state. In the event that there are
disturbances in the magnetic field due to hard or soft iron effects, then these registers allow for further
compensation. These registers can also be used to compensate for significant changes to the
magnetometer bias, gain, and axis alignment during installation. Note that this magnetometer
compensation is separate from the compensation that occurs during the calibration process at the factory.
Setting this register to the default state of an identity matrix and zero offset will not eliminate the
magnetometer gain, bias, and axis alignment that occur during factory calibration. These registers only
need to be changed from their default values in the event that hard/soft iron compensation needs to be
performed, or changes in bias, gain, and axis alignment have occurred at some point between the times
the chip was calibrated at the factory and when it is used in the field.
{
𝑋
𝑌
𝑍
} = [
𝐶00 𝐶01 𝐶02
𝐶10 𝐶11 𝐶12
𝐶20 𝐶21 𝐶22
] ∙ {
𝑀𝑋 − 𝐵0
𝑀𝑌 − 𝐵1
𝑀𝑍 − 𝐵2
}
The variables
{𝑀𝑋, 𝑀𝑌, 𝑀𝑍}
are components of the measured magnetic field. The {X, Y, Z} variables are
the new magnetic field measurements outputted after compensation for hard/soft iron effects. All twelve
numbers are represented by single-precision floating points.
