BEI Sensors THK4 - Manual (Page 5)

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1. Introduction
This manual explains how to install and
configure the MAGNETOCODE absolute rotary
encoder with CANopen interface applicable for
both military and industrial applications with
CANopen interface. The products are fully
compliant with standard DS406.
Measuring System
Magnetic rotary encoder determine
positions using the Hall effect sensor
technology developed for the automotive
mass market. A permanent magnet fixed to
the shaft generates a magnetic field that is
sampled by the Hall sensor, which
translates the measured value into a unique
absolute position value.
To register revolutions even when no
voltage is applied, energy from the turning
of the shaft must suffice for proper
operation. An innovative, patented
technology makes this feasible even at low
rotational speeds and through long
standstill periods – a Wiegand wire ensures
that the magnetic field can only follow the
turning of the shaft in discrete steps. A coil
wound on the Wiegand wire receives only
brief, strong voltage spikes, which prompt
the reliable recognition of each revolution.
Typical Applications:
• Packing Machines
• Mobile Machines
• Wind Mills
• Medical Equipment
1.1 General CANopen Information
The CANopen system is used in industrial
applications. It is a multiple access system
(maximum: 127 participants), which means that
all devices can access the bus. In simple terms,
each device checks whether the bus is free, and
if it is the device is able to send messages. If two
devices try to access the bus at the same time,
the device with the higher priority level (lowest
ID number) has permission to send its message.
Devices with the lowest priority level must delay
their data transfer and wait before retrying to
send their message. Data communication is
carried out via messages. These messages
consist of 1 COB-ID followed by a maximum of 8
bytes of data. The COB-ID, which determines
the priority of the message, consists of a
function code and a node number. The node
number corresponds to the network address of
the device. It is unique on a bus. The function
code varies according to the type of message
being sent:
 Management messages (LMT, NMT)
 Messaging and service (SDOs)
 Data exchange (PDOs)
 Layer Setting Services (LSS)
 Predefined messages (synchronization,
emergency messages)
The absolute rotary encoder supports the
following operating modes: