AHRS400 Series User’s Manual
Page 18
Doc# 7430-0004-01 Rev. A
voltage at the sensor output. To convert the analog output to a sensor value
use the following relation:
rate
=
AR
*1.5 *
V
out
(V) / 4.096 V
where
rate
is the actual measured rate in units
°
/s,
AR
is the angular rate
range of the sensor and
V
out
is the measured voltage at the analog output.
For example, if your DMU has a ±100
°
/s rate sensor, and the analog output
for that sensor is –1.50 V, the value of the measurement is 100 (
°
/s)*1.5*(-
1.50)/4.096 = -54.9
°
/s.
In scaled measurement mode, pins 12 – 14 represent the magnetic vector
measured by the DMU. To convert the voltage to magnetic field in Gauss,
use the following relation:
mag
=
MR
*1.5 *
V
out
(V) / 4.096 V
where
mag
is the magnetic field measured along that axis,
MR
is the
magnetometer range, and
V
out
is the voltage measured at the analog output.
MR
is 1.25 for the AHRS.
In angle mode, the AHRS outputs the pitch, roll, and yaw angles on pins 12
- 14. The analog outputs are created by the D/A. The voltage output will
be in the range ± 4.096 V. The output is scaled so that full scale is 180
°
for
both roll and yaw. Pitch is scaled so that full scale is 90
°
. To convert the
voltage to an actual angle, use the following conversion:
angle
=
FA
*
V
out
(V) / 4.096 V
where
angle
is the actual pitch, roll or yaw angle in degrees,
FA
is the full-
scale angle, and
V
out
is the analog voltage measured.
FA
is 180
°
for roll
and yaw;
FA
is 90 for pitch.
3.10 Magnetic Heading
Magnetic north is the direction toward the magnetic north pole; true north is
the direction towards the true North Pole.
The AHRS 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 AHRS 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:[email protected]
SUNSTAR自动化 http://www.sensor-ic.com/ TEL: 0755-83376489 FAX:0755-83376182 E-MAIL:[email protected]
