FeiYu Tech FY-ARHS-1200A - Manual (Page 8)

GuiLin FeiYu Electronic Technology Co., Ltd
GuiLin FeiYu Electronic Technology Co., Ltd http://www.feiyudz.cn E-mail: [email protected]
Page 7
4、Magnetic field calibration
FY-AHRS-1200A will be started magnetic compensation calibration procedures once the installation
finished. The magnetic field compensation process in the module's firmware determines the magnetic field
calibration impact of the installation of platform, so even if the FY-AHRS-1200A is installed on the steel
device (for example, a vehicle), its still can provide accurate readings. FY-AHRS-1200A has the
compensation effect only in a limited interference range. Range value of magnetometer is between minus
100 and plus 100 m-Teslas which is approximately twice the magnetic force in middle latitude northern
hemisphere,. If the disturbance value of the magnetic field more than plus or minus 50 m-Teslas, the
magnetometer could reach saturation and block compensation.
Magnetic compensation function is semi-automatic. Once started, FY-AHRS-1200A will collect data
automatically from every position of the circumference. After complete this work, the module will calculate
the correction factor to compensate for the near magnetic field abnormalities, and to store the corrected
value in the permanent memory. After the compensation process, the corrected value will be merged into the
subsequent azimuth data.
If necessary, the compensation process can be repeated several times. When began to run the test
program, please note: The magnetic objects (such as the nearby mobile phones, structural steel and buried
underground pipelines) may lead to azimuth errors. If the FY-AHRS-1200A is installed in a vehicle, it will
encounter the magnetic field anomaly; this is why there is a magnetic compensation procedure. However,
for some bulky magnetic properties are very likely to distort the earth’s magnetic field, even the process of
magnetic compensation happened in a long distance.
Magnetic declination and bias of installation is the most important parameter values, which can be
entered into the module by the host. Usually, when power-on, the module will automatically set the value of
magnetic declination and bias to 0. This can be changed through software commands, and the value is still
valid after restarted.
Magnetic declination (also known as magnetic variable) is the angle between true north and magnetic
north. Azimuth bias is defined as the level angle deviation between the module's forward axis (X axis) and
the reference axis of installation platforms. Azimuth bias is a constant, which is decided the module
mechanical placement and installation elements. Magnetic declination and Azimuth bias will affect the
accuracy of the Azimuth observation.The module should use these two corrected values, and add it to the
magnetic field course deviation angle correction option.
According to usual practice, both the mark symbol of magnetic declination and azimuth bias used in
the east are belonging to positive sign. For example, if magnetic north is the east of true north, magnetic
declination is positive. For example, the local magnetic declination is -6 °, the install bias is -2 °, and then
the magnetic field course deviation angle correction option should fill in the 8 °.
In the implementation of the "Start calibration of XY-axis magnetic field", you need to place
FY-AHRS-1200A horizontally (the X-Y plane of FY-AHRS-1200A is parallel with the ground level. At the
same time, the right side of Z-axis being faced down with the ground water level vertically), and rotate the
module clockwisely, keep it stable circular movement. If the FY-AHRS-1200A is installed in a vehicle, the
above steps are completed by rotate the vehicles slowly on the horizontal ground.