PNI SENtral - Manual (Page 5)

PNI Sensor Corporation Doc #1018049 R03
SENtral Technical Data Sheet Page 4
1.2 SENtral Functional Description
Figure 1-1 provides a diagram of SENtral’s primary functional blocks, and a brief description
of these functional blocks follows.
Figure 1-1: SENtral Block Diagram

Quaternion generates the orientation output, where the actual orientation outputs can
be quaternions or Euler angles (heading, pitch, & roll). The outputs are updated at a
rate limited to the gyro output data rate (ODR), to a maximum of 400 Hz.

Kalman Update fuses data from the 3-axis gyroscope, 3-axis accelerometer, and 3-
axis magnetometer, plus data from the magnetic anomaly determination and
continuous auto-calibration blocks to generate intelligent orientation updates. The
Kalman update involves a sophisticated multi-state Kalman algorithm.

Continuous Hard and Soft-Iron Auto-Calibration. SENtral is the only product in
the market that auto-calibrates for both hard-iron and soft-iron magnetic distortions.
While others may calibrate for hard-iron distortion, soft-iron distortion is more
difficult to correct for, and it can be caused by EMI shielding tape and other shielding
materials widely used in mobile and consumer electronic devices. It is important to
correct for soft-iron distortions since these can contribute up to 90° of error.
Additionally, since a host system’s magnetic signature can change over time and
temperature, SENtral’s continuous auto-calibration ensures accuracy all the time.