BOURNS EM14

Bourns® Model EMS22
Non-Contacting Magnetic Encoder
Sensors & Controls Product Brochure
Bourns® Model EMS22 Product Description
Bourns® Model EMS22 is a non-contacting rotary
The EMS22 non-contacting encoder is ideal for
magnetic encoder with a Hall Effect application-
use in harsh environments where extreme levels of
specific standard product (ASSP) capable of
temperature, moisture and particles are present. The
producing four distinct output waveforms. These
outstanding performance of this device is attributed
waveforms include 2-bit quadrature up to 256 PPR*,
to the non-contacting technology and superior
Step/Direction up to 512 PPR, Pulse-Width
performance of the austriamicrosystems® AS5040
Modulated (PWM) output with 1024 positions, and
Hall Effect ASSP. In addition, this product is sealed
Absolute with 1024 positions.
to IP** 65 with an optional upgrade to IP 67.
Model EMS22 is available in both a 3.3 and 5.0 Vdc
The EMS22 is RoHS compliant in accordance with
supply voltage and is offered in two different
Directive 2002/95/EC of the European Parliament
versions. This product has the capability of rotating
and Council of 27 Jan 2003 on the restriction of the
up to 10,000 RPM while maintaining code accuracy,
use of certain hazardous substances in electrical and
making it suitable for MMI applications such as
electronic equipment.
industrial automation. This performance is achieved
by utilizing dual ball bearings in the construction of
This model is produced and assembled utilizing
the device, resulting in extended rotational life up to
state-of-the art production equipment along with
100,000,000 shaft revolutions (beyond 100,000,000
lean principles to provide our customers with a high
shaft revolutions in some configurations).
performance product at a competitive price.
* Pulses per Revolution
** Ingression Protection
What is Hall Effect?
Discovered by Edwin Hall in 1879, Hall Effect refers
to the potential difference on opposite sides of a
bar-shaped conducting or semi-conducting material
(Hall element). This potential difference (voltage) is
produced by a magnetic field applied perpendicular
to the Hall element through which an electric current
flows. Figure 1 is provided to clarify this concept by
illustration. Figure 2 demonstrates two different states
of the AS5040 ASSP as the magnet rotates in close
proximity to the ASSP.
Figure 1: Hall Effect Concept
EMS22 Output Waveforms
Quadrature: This output waveform is the
Absolute: Absolute output refers to the absolute
most common among all contacting and non-
angular position. This type of output is especially
contacting encoders. Quadrature, also known as
useful for applications where the absolute position
2-bit quadrature or incremental, is often used to
of a device, such as a camera, is necessary to locate
determine magnitude (count) and direction (up/
an object. Also with 1024 distinct angular positions,
down) by an external interface circuit. EMS22
the EMS22 offers very high resolution indexing at
comes equipped with such capability; an external
every 0.35 °. This type of output code is not affected
interface circuit is not required. It also offers an
by a power outage to the encoder since each angular
indexed output with an adjustable width of one or
position of the encoder has a unique code.
three times the absolute position value that can be
used for counting the shaft rotation.
PWM: Pulse-Width Modulation is another form
of absolute waveform that utilizes the square wave
Direction/Step: This output is very similar to the
output generated by the sensor to control the
quadrature waveform but offers up to 512 PPR, as
duty cycle of the output at different desired shaft
opposed to 256 PPR in quadrature. This output can
positions. The EMS22 encoder can generate pulse
be used in incremental counting applications where
widths as low as 1 µs, and as high as 1024 µs in a
a better resolution is desired. Indexing output is also
complete signal period of 1025 µs. Some advantages
available with a Direction/Step output waveform.
of using this output waveform over other output
types include immunity to noise and faster data
acquisition.
Figure 2: AS5040 ASSP in Two Different States
How the EMS22 Rotary Magnetic Encoder Works
The EMS22 produces a sinusoidal signal by rotation
of the magnet in close proximity to the ASSP, based
on the Hall Effect phenomenon. The sinusoidal
signal is then converted to the desired output
waveform by the ASSP that is preprogrammed at the
factory to produce one of the output signals below:
• Quadrature
• Direction/Step
• PWM
• Absolute
Figure 3 below shows the steps involved in
generating an output signal.
Rotation of the magnet
over the ASSP produces
the sinusoidal signal
Desired output
signal is generated
via ASSP
Shaft is rotated
via MMI or HMI
3.3 or 5.0 Vdc
supply voltage is
applied to the encoder
Figure 3: Output Signal Generation Steps in EMS22
Why Use an EMS22 Magnetic Encoder?
The EMS22 can offer enhanced reliability in harsh
the EMS22 can have more than 50 times the life
environmental conditions such as mud, dust, grease,
expectancy of traditional contacting encoders.
oil, water and dirt, giving this product an edge in
performance over traditional optical and contacting
The designer and end user can expect cycle
encoders. Figure 4 illustrates examples of harsh
life performance without degradation of signal
environments.
accuracy, a clear advantage over encoders that use
optical or contacting technology.
In addition, there are no contacting parts between
the magnet and the ASSP to degrade the life
expectancy of this type of encoder. As a result,
Figure 4: Examples of Harsh Environments
EMS22 Features and Benefits
Design engineers with constraints such as cost, space,
Another great capability of this product is the chip-select
circuit complexity and resolution will appreciate the
option. This option allows the interrogation of each encoder
unique features and benefits of the Model EMS22.
individually by the microprocessor. Unlike daisy-chain, this
feature takes less time to execute, ultimately enhancing the
EMS22 non-contacting rotary magnetic encoders can be
speed of the control loop response.
interconnected in a daisy-chain configuration for a serial
read-out option. This option is beneficial where memory
If temperature variation is a critical factor in the application,
overhead and space for wiring each individual encoder
the EMS22 offers excellent performance in a wide
separately is critical in the construction of a control device
temperature range, from - 40 °C to + 125 °C (- 40 °F to
as illustrated in Figure 5. The output of this configuration
+ 257 °F). This feature is suitable for applications in extremely
is the combined output of each individual encoder
cold and hot temperature conditions that can affect the
connected in series to the microprocessor.
output performance of optical and contacting encoders.
Microprocessor
EMS22
Data Input
Prog.
Data
Input
Data
Input
Chip
Select
CLK
EMS22
Data
Input
EMS22
Prog.
Data
Input
Chip
Select
CLK
Data
Input
Chip
Select
Prog.
Data
Input
CLK
CLK
Chip Select
Figure 5: Daisy-Chain Hardware Configuration
Designers can choose from a variety of output signals to
Table 1 below provides a comparison of the various
fit their application needs, whether it is a simple counter,
technologies, output types, supply voltages, and resolution
or precision sensing. The EMS22 is capable of operating
that can be achieved with each Bourns® Encoder model
with either a +5.0 Vdc supply voltage, or the more energy
family.
efficient +3.3 Vdc supply voltage.
Bourns®
Encoder Model
Technology
Output Type(s)
Supply Voltage
(Vdc)
Resolution
(PPR)/ States*
EAW (ACE)
Contacting
Absolute
3.3 & 5.0
128*
ECW
Contacting
Quadrature
3.3 & 5.0
6, 9, 12, 24, 36
EM14
Optical
Quadrature
5.0
8, 16, 32, 64
EN
Optical
Quadrature
5.0
25, 50, 64, 100, 125, 128,
200, 256
EMS22
Magnetic
Quadrature
3.3 & 5.0
32, 64, 128, 256
EMS22
Magnetic
Direction/Step
3.3 & 5.0
64, 128, 256, 512
EMS22
Magnetic
Absolute/PWM
3.3 & 5.0
1024*
Table 1: Comparison of Various Bourns® Models
Applications
Typical applications of the Bourns® EMS22 Rotary
Magnetic Encoder with Hall Effect sensors include but are
not limited to:
• Audio mixer and broadcasting equipment
• Office equipment: printers, scanners, copiers
• Brushless DC motors
• Power seating position indicators
• Car audio
• Power tools
• Car navigation
• Pressing and punching machines
• Cursor position sensing in oscilloscopes
• Replacement of optical encoders
• Food processing and packaging
• Replacement of potentiometers
• Forklifts and material handling equipment
• Robotics
• Gas pedal position sensing
• Servomotor control
• Headlight position controls
• Steering wheel position sensing
• Level setting for ultrasound imaging devices
• Light dimmers
• Marine applications
• Medical devices (non-life critical)
• Metal cutting saws
• Metal working and instrumentation
Modification Capabilities
The EMS22 Rotary Magnetic Encoder with Hall Effect
sensor can be customized to suit your application and
design needs. These customizations include but are not
limited to:
• Analog output to 360 degrees
• Brushless DC motor commutation
• Custom cable and connectors
• Custom shaft and bushing configurations
• Customized electrical angle from 45 to 360 degrees
• High temperature version up to +150 °C
• Sealed to IP 67
Please contact your local Bourns Sales Representative or
Field Application Engineer for additional information.
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www.bourns.com
Bourns® products are available through an extensive global network of representatives and distributors.
To obtain technical applications assistance, a quotation, or to place an order, contact a Bourns representative in your area.
Specifications subject to change without notice. Actual performance in specific customer applications may differ due to the
influence of other variables. Customers should verify actual device performance in their specific applications.
“austriamicrosystems” is a registered trademark of austriamicrosystems AG in the U.S. and other countries.
“Bourns” is a registered trademark of Bourns, Inc. in the U.S. and other countries.
COPYRIGHT© 2008, BOURNS, INC. • LITHO IN U.S.A. • WAG • 02/08 • 2M/SC0676