AHRS500GA Series Operator’s Manual
Doc# 7430-0060-02 Rev. A
Page 11
Each data packet will begin with a two -byte header (hex AA 55) and end
with a two-byte checksum. The checksum is calculated in the following
manner:
1. Sum all packet contents
except
header and checksum.
2. Divide the sum by hex FFFF.
3. The remainder should equal the checksum.
The packet also contains the model type configuration number, and the BIT
word output. Please refer to section 3.3.3 for details about t he BIT word
processing.
3.6
Timing
The default AHRS500GA data output rate is 100 samples per second.
Depending on the model configuration chosen, the system output sample
rate can be set to a different constant value.
In some applications, using the AHRS500GA’s digital output requires a
precise understanding of the internal timing of the device. The processor
internal to the AHRS500GA runs in a loop - collecting data from the
sensors, processing the data, and then collecting more data. The data is
reported to the user through a parallel process.
The unit goes through three processes in one data cycle. First, the sensors
are sampled. Second, the unit processes the data for output. After
processing the data, the AHRS500GA will make another measurement
while presenting the current measurement for output. Third, the unit
actually transfers the data out over the RS-232 port.
3.7
Magnetic Heading
Magnetic north is the direction toward the magnetic north pole; true north is
the direction towards the true North Pole.
The AHRS500GA yaw angle output is referenced to magnetic north. The
direction of true north will vary from magnetic north depending on your
position on the earth. The difference between true and magnetic north is
called declination or magnetic variance. You will need to know your
declination to translate the AHRS500GA magnetic heading into a heading
referenced to true north.
SUNSTAR传感与控制 http://www.sensor-ic.com/ TEL:0755-83376549 FAX:0755-83376182 E-MAIL:szss20@163.com
SUNSTAR自动化 http://www.sensor-ic.com/ TEL: 0755-83376489 FAX:0755-83376182 E-MAIL:szss20@163.com
