Attitude and Heading Reference System AHRS-S305

The AHRS-S305 attitude reference provides all the same data as our AHRS-E304. It uses smaller MEMS gyroscopes so the entire sensor suite can fit into a smaller package.


  • Solid State, Strapdown System
  • Small Size
  • Low Cost, Low Power
  • Rugged, High Reliability
  • Analog and RS-232 Serial Outputs
  • PC Heading Calibration
  • One Year Limited Warranty
  • Engineering Support

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The AHRS-S305 is Watson Industries’ newest Attitude and Heading Reference System. Standard for an attitude gyro system, the AHRS-S305 has a sensor package that consists of three solid state angular rate gyros, three accelerometers, and a triaxial fluxgate magnetometer used as a heading reference. This AHRS differs from our other inertial gyro packages because this sensor uses MEMS gyros that are smaller and less expensive than our line of VSG angular rate sensors. This makes the AHRS-S305 more economical and half the size of the AHRS-E304 attitude reference which uses VSG gyros for enhanced accuracy and signal stability.

The signals from three solid state angular rate gyros are coordinate transformed and then integrated to produce attitude and heading outputs that reflect normal attitude coordinates. These attitude and heading signals are compared to the accelerometers and the fluxgate magnetometer to derive gyro drift error. These errors are filtered over a long time constant and are used to adjust system biases so that the long-term convergence of the system is to the vertical references and the magnetic heading reference. A velocity input can be used to improve the overall stability and accuracy of the system by calculating centrifugal forces and velocity changes on the vertical reference and compensating for them.

This is a microprocessor-based system using a 16 bit A/D converter, a 14 bit D/A converter and an RS-232 interface. The analog attitude and heading outputs are updated 71.11 times per second. The serial interface is highly configurable and provides access to almost all operational parameters.

The AHRS-S305 is useful for land and sea applications. Some examples include control and stabilization of remote piloted subs or antennas, robotics research, and road surface measurement. See our Applications Index for a more complete listing of applications.



Range: Bank ±180°
Range: Elevation ±90°
Resolution: 0.02° Binary mode (14 bit)
Analog Scale Factor: 18°/V ±10V Bank
±5V Elevation
Accuracy: Static ±0.5°
* Accuracy: Dynamic 2%

Magnetic Heading

Range: 0° – 360°
Resolution: 0.02° Binary mode (14 bit)
Analog Scale Factor: 18°/V ±10V Output
Accuracy: Static ±1°
* Accuracy: Dynamic 2%

Angular Rate

Range: Roll, Pitch, Yaw ±100°/sec
Resolution: 0.025°/sec Binary mode (14 bit)
Analog Scale Factor: 10°/sec/V ±10V Output
Scale Factor Accuracy: 2%
Bias: Roll, Pitch, Yaw < 0.3°/sec
Non-Linearity: < 0.05% Full scale range
Bandwidth: 20 Hz


Range: X, Y, Z ±10g
Resolution: 4mg
Scale Factor Accuracy: 1%
Bias: < 10mg
Non-Linearity: 0.1% Full scale range
Bandwidth: 3 Hz


Range: X, Y, Z ±1000 mGauss
Resolution: 0.1 mGauss Binary mode (14 bit)
Scale Factor Accuracy: 1%
Bias: < 5 mGauss
Non-Linearity: < 0.01% Full scale range
Bandwidth: 10 Hz


Temperature: Operating -40°C to 85°C
Temperature: Storage -55°C to 85°C
Vibration: Operating 2.5g rms 20 Hz to 2 KHz
Vibration: Survival 10g rms 20 Hz to 2 KHz
Shock: Survival 500g 10mS ½ sine wave


Frame Rate: 71.1 Hz Maximum
Startup Time: Data 5 sec
Startup Time: Fully operational 10 sec
Input Power: 10 to 35VDC 2.8W
Input Current: 215mA @ 12VDC 115mA @ 24VDC
Input Velocity: (Optional) ±10VDC Full scale (±800kph)
Digital Output: RS-232
Analog Output: ±10VDC
Analog Output Impedance: 300 Ohm Per line


Axis Alignment: < 0.25°
Size: Including Mounting Flanges 3.24″W x 5.78″L x 2.38″H 8.2 x 14.7 x 6.0 (cm)
Weight: 21 oz (1.3 lb) 595 grams (0.6 Kg)
Connection: 25 pin male “D” subminiature
* Assumes accurate velocity data.
Actual accuracy can be calculated as the listed percentage multiplied by the change in value over the entire dynamic maneuver.
Static heading accuracy is dependent on the magnetic environment.
This sensor will meet or exceed this spec within the 48 contiguous United States.
Specifications are subject to change without notice.
This product may be subject to export restrictions. Export Classification ECCN 7A994.



Title File Type
AHRS-S305 Spec Sheet pdf Download
AHRS-S305 Owner’s Manual pdf Download