UMAX0608XX‐1000. Tri‐Axial J1939 CAN Inclinometer. Version 9B
Page: 6-66
2 INCLINOMETER DESCRIPTION
The inclinometer is designed to measures pitch and roll inclination angles in a full ±180-degree
orientation range. The unit can also output gravity angle and unit accelerations in three
orthogonal directions.
The inclinometer transmits data over CAN bus using a standard J1939 protocol. In addition to
the CAN bus, the AX0610000 inclinometer can output data using three analog signal outputs.
The J1939 inclinometer can operate at standard 250kbit/s and 500kbit/s baud rates or non-
standard 667kbit/s and 1000kbit/s (1Mbit/s) baud rates. The required baud rate is detected
automatically upon connection to the CAN network.
1
1
Inclinometers with firmware V1.xx…6.xx could operate only at 250kbit/s baud rate, and with firmware
V7.xx…8.xx – at 250, 500, and 1000 kbit/s baud rates.
The inclinometer can be configured through a set of configuration parameters to fit the user-
specific application requirements using Axiomatic Electronic Assistant
®
software.
2.1 Theory of Operation
2.1.1 Unit Coordinate System
The inclinometer uses a standard right-handed Z-down Cartesian coordinate system, see
Figure 1.
X‐ Axis
Y ‐ Axis
Z‐ axis
φ ‐ Roll
θ ‐ Pitch
Ψ ‐ Yaw
a
x
a
z
a
y
Figure 1. Inclinometer Coordinate System
The arrows in Figure 1 represent a direction of motion that produces a positive change of the
parameter. For a
x
, a
y
, a
z
accelerations, the positive acceleration direction is the same as the
axis direction. For
𝜃, 𝜙, 𝜓
rotation angles the positive direction is contraclockwise about the axis
of rotation (right-hand rule).
The Z-down coordinate system is described by in the SAE J670 standard for automotive
applications. It is used in SAE J1939 slope sensor PGN definitions. This system is similar to
the NED (North-East-Down) coordinate system used in aerospace and navigation, but without
reference to the cardinal directions.
2.1.2 Unit Reference Frames
Several Z-down coordinate systems or frames are used to describe the inclinometer
orientation.
