ELECTROMECHANICAL SOLUTIONS
AME04
Magnetic
Technology
SINGLE TURN
ABSOLUTE MAGNETIC ENCODER
PRESENTATION
The absolute encoder
AME04
is the smallest rotary sensor
based on magnetic technology designed by
EXXELIA
GROUP
. Its
compactness makes this product a cost-effective solution
for applications in confined areas and it can be ideally used
for automatic control, on-line gauging, in-process monitoring
systems, etc.
Various output protocols are available in order to match most
applications.
High temperature
up to +125°C
SSI / FSSI
interface
Miniaturization
Light weight
Low profile
GENERAL DATA
Resolution
Accuracy
Maximum rotation speed
Starting torque
Weight (without cable)
Up to 16 bits
Up to ± 20’
600 rpm
≤ 0.1 N.cm
10 g max.
ENVIRONMENTAL DATA
Operating temperature
Storage temperature
Sealing
Vibrations
Shocks
Magnetic field susceptibility
For other specifications, please contact us
Up to –55°C to +125°C
–55°C to +125°C
IP 40
20 g, 1.5 mm, 10 Hz to 2 kHz
50 g, ½ sine, 11 ms.
20 mT max.
DIMENSIONS (in mm)
Ls
±0.5
14
±0.2
Ø 9.525
–0.013
0
Ø 3.175
–0.013
6 x AWG32 wires
Length
Lw
0
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28
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Page revised - Version 05/16
ELECTROMECHANICAL SOLUTIONS
SINGLE TURN
ABSOLUTE MAGNETIC ENCODER
STANDARD ELECTRICAL DATA
Power supply
Maximum consumed current
Output signals
Maximum operating frequency
For other specifications, please contact us
AME04
+5 V
DC
± 5%
30 mA
RS422/485
2 MHz (SSI) / 4 MHz (FSSI)
CONTACTLESS POSITION SENSORS
•
W
N
W:
RoHS compliant
Page revised - Version 05/16
ELECTRICAL INTERFACE
RS422/485 Interface
User
Encoder
150
Wiring diagram
Red
Encoder output
Clock
Black
Yellow
White
Blue
Green
V
CC
GND
CLK
CLK
DATA
DATA
150
Data
HOW TO ORDER
Resolution
AME04
••
10
16
Accuracy
•••
040
020
Direction
of signals
••
CW
KW
Protocol
1
••
S1
FS
Temperature
range
••
ST
MT
HT
XT
Mechanical
coupling
••
01
02
XX
Wire length Shaft length
RoHS
(Lw)
(Ls)
compliance
•••
250
TBD
•••
125
TBD
ST:
Standard temp.
–40°C to +85°C
040:
±40’
Standard
with coupling
020:
±20’
CW:
Clockwise
KW:
Counter
clockwise
S1:
SSI
FS:
FSSI
Standard
SSI2 compatible
MT:
Medium temp.
–45°C to +105°C
HT:
High Temp.
–55°C to +115°C
XT:
Extended Temp.
–55°C to +125°C
1: Please refer to «Encoder Handbook» available on
EXXELIA
GROUP
website.
2: For further information, please contact us.
01:
Without coupling
02:
Standard coupling
1
XX:
Custom coupling
2
10
to
16
bits
250:
250 mm
Standard
125:
12.5 mm
Standard
N:
TBD:
TBD:
Non compliant
To Be Defined To Be Defined
by the customer by the customer
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Contactless Position Sensors general information
1. INTRODUCING EXXELIA
GROUP
ENCODERS
Encoders are sensors that generate digital signals in response
to movement. Encoders come with two outlines: rotary and
linear
. Both types sense mechanical motion and translate the
information (velocity, position, acceleration) into useful data.
A contactless technology
To address demands for longer service life and with its
strong track record in contact technology position sensors
(potentiometers), Electromechanical Solutions SBU has been
developing own-brand contactless sensors for nearly 10 years.
These sensors are absolute and incremental optical encoders,
magnetic technology and inductive sensors.
Absolute optical or magnetic encoders: absolute optical
encoders are position sensors that use optical signals to
identify an absolute angular position. The
EXXELIA
GROUP
encoders offer very high performance levels for a very small
footprint:
• high precision (<30 arcsec),
• high resolution (up to 21 bits),
• highly thin (10mm),
• EMI EMC compatibility
Incremental optical or magnetic encoders: absolute optical
encoders are position sensors that use optical signals to
identify an absolute angular position. Incremental encoders
have to be initialized by a first turn to produce an absolute
position.
Applications:
Aeronautics, Defense, Railway, Medical, Oil
exploration, Telecommunications
EXXELIA
GROUP
encoders can also be easily combined with other
functions like Slip rings or rotary joints (FORJ, HF...) in complete
proprietary systems.
conveys or alternatively blocks the light emitted by the source;
the scale or the disk is acts in fact as a beam switch. The photo-
receiver generates an electrical signal, which is processed and
analyzed in order to allow encoding the system position.
An optical encoder consists of three major subsets:
• Encoder housing.
• Optical block: consisting of an emission system, an
optical coding system and a detection system. It
generates the position function signal.
• Electronics block: it allows amplifying, converting and
processing the signal.
Photo-emitter
Optical disk
Reticles
Photo-receivers
Figure 1: Incremental principle
Photo-receivers
Reticles
2. SENSING TECHNOLOGY
Encoders can use either optical or magnetic sensing
technology.
Optical sensing provides high resolutions, high operating
speeds, and reliability, long life operation in most environments.
Magnetic sensing, often used in rugged applications provides
good resolution, high operating speeds, and maximum
resistance to dust, moisture, and thermal and mechanical
shock.
Optical Encoders: principles
Optical encoders’ principle of operation is relatively simple; a
light source (photo-emitter) sends light through a mobile disk
or scale, consisting of a succession of opaque and transparent
parts, on photo-receivers. When the disk or the scale moves, it
Coding disk
Photo-emitters
Figure 2: Absolute principle
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GENERAL TECHNICAL DATA
ELECTROMECHANICAL SOLUTIONS
ELECTROMECHANICAL SOLUTIONS
Contactless Position Sensors general information
Optical encoders use a glass disk with a pattern of lines
deposited on it, a metal or plastic disk with slots (in a rotary
encoder), or a glass or metal strip (in a
linear
encoder). Light
from a LED shines through the disk or strip onto one or more
photodetectors, which produce the encoder’s output.
industrial environments, as well to shock and vibrations.
Photo-emitters
Linear coding scale
Fig. 4a
Fig. 4b
Figure 4: Magnetic Sensor principles:
a) On axis technology with a bipolar magnet
b) odd axis technology with a multipolar ring
Reticles
4. ABSOLUTE OR INCREMENTAL CODING?
INCREMENTAL CODING
Photo-receivers
Figure 3: Linear principle
Incremental encoders provide a specific number of equally
spaced pulses per revolution (PPR) or per inch or millimeter of
linear motion.
3. MAGNETIC ENCODERS: PRINCIPLES
The position sensors which use the detection of a magnetic
field generally work following the same principle:
A magnetic field is generated thanks to a permanent magnet or
an electromagnet. The distribution in the space of this magnetic
field is not homogeneous. Depending on the relative positions
of the magnetic source, the sensors cells and a possible
ferromagnetic third element, the magnitude of the field will be
different. The measured value is then analysed as a function
of the specific geometry in order to recover the information of
position.
Among magnetic encoders we can distinguish several
technologies which are using this principle to convert magnetic
field into a physical quantity useful in electronic devices
(typically current or tension). The most common are inductive
encoder, magneto-resistive encoder and Hall effect encoder.
Magnetic encoders are typically robust and non-sensitive to
environmental stress like shocks, vibrations, and chemical
substances. In order to protect the measurement against a
variation of the external magnetic field (especially next to
motors), it is possible to add a magnetic shielding with specific
materials and to carry out differential measurements.
Magnetic encoders constitute miniature long-life cost-effective
sensors. Magnetic sensing technology is very resistant to
dust, grease, moisture, and other contaminants common in
A
B
Figure 5: A and B quadrature signals
For applications that do not require detection sensing, a single
channel output is used. But in most cases, two channels A
and B, 90 electrical degrees out of phase are used. Those two
channels allow a detection of the direction of motion (See
Figure 6). This is useful for processes that can reverse, or must
maintain steady position when standing still or mechanically
oscillating.
CW
A
B
A
B
CCW
Figure 6: Determination of the direction of movement
The quantity of positions that can be detected depends on
electronic processing from channels A and B (see Figure 7). In
the case the disk has N periods or “bars”:
If processing system only detects leading (or trailing) edges of
channel A (or B), then the resolution is equal to the number N.
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Contactless Position Sensors general information
If the system detects leading and trailing edges of channel A
(or B), or if it detects leading or trailing edges of channels A and
B, then the resolution is equal to 2N.
If processing system detects leading and trailing edges of the
channels A and B, then the resolution is 4N.
In some configurations, it is even possible to electronically
interpolate more precisely this signal and achieve up to 50N
resolution.
To determine a position, incremental encoders need an
initialization step that is a lap or a movement to find the “zero”
reference or home position. After this step, each pulse will be
accumulated into a counter. In case of a power interruption or
corruption by electrical transients, the count is lost and the
initialization step should be done again.
Signal A only
Signal A + B
“zeroing” (seekers, flight commands, radar mechanics...).
How to easily understand the difference between
incremental and absolute encoders?
A well-known image is that the difference between
incremental and absolute encoders is similar to the
difference between a stop watch and a clock. A stop watch
measures the incremental time that elapses between its
start and stop, just like an incremental encoder will provide
a known number of pulses relative to a movement. If you
knew the actual time when you started the watch, you can
tell what time it is later by adding the elapsed time value
from the stop watch. For position control, adding incremental
pulses to a known starting position will measure the current
position. When an absolute encoder is used, the actual
position will constantly be transmitted, just as a clock will
tell you the current time.
A
A
B
5. SSI / FSSI
SSI is a synchronous, point to point, serial communication
channel for digital data transmission. Synchronous data
transmission is one in which the data is transmitted by
synchronizing the transmission at the receiving and sending
ends using a common clock signal. Since start and stop bits
are not present, this allows a better use of data transmission
bandwidth for more message bits and makes the whole
transmission process simpler and easier. The clock needs its
own bandwidth and should be included when determining the
total bandwidth required for communication between the two
devices.
In general, as mentioned earlier, it is a point to point connection
from a master (Microcontroller) to a slave (rotary encoders).
The master controls the clock sequence and the slave transmits
the current data/value through a shift register. When invoked
by the master, the data is clocked out from the shift register.
The master and slave are synchronized by the common clock
of the controller.
The CLOCK and DATA signals are transmitted according to RS-
422 standards. RS-422, also known as ANSI/TIA/EIA-422-B, is a
technical standard that specifies the electrical characteristics
of the balanced voltage digital interface circuit. Data are
transmitted using balanced or differential signaling and the
CLOCK and DATA lines are basically twisted pair cables.
FSSI is the same synchronous interface but includes a start bit
and is more flexible for other options (Alarm bit, ID encoder....).
The maximum bandwidth is 4 MHz.
Resolution = N
Resolution = 2N
Resolution = 4N
Figure 7: Resolution of incremental encoders
This “zero” or home position may be output as a signal known
as the “marker,” “index,” or “Z channel.”
Incremental encoders are principally used in applications
where relative movement is required, such as machine or
process control, robotics...
ABSOLUTE CODING
Absolute coding is basically different than incremental coding.
Every position of an absolute encoder is unique. Unlike
an incremental encoder, where position is determined by
counting pulses from a zero mark or home base, the absolute
encoder reads a system of coded tracks to establish position
information.
Absolute encoders do not lose position when power is removed.
Since each position is unique, true position verification is
available as soon as power is up. It is not necessary to initialize
the system by returning to home base.
An absolute encoder’s resolution is defined as the number of
bits in its output word. This output can be in natural binary or
in gray code, which produces only a single bit change at each
step to reduce errors.
Absolute encoders will be used when the measurement is
critical and the application cannot afford an initializing step for
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GENERAL TECHNICAL DATA
ELECTROMECHANICAL SOLUTIONS
Embedded System
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