Bourns Model EMS22
Non-Contacting Magnetic Encoder
®
Sensors & Controls Product Brochure
Bourns® Model EMS22 Product Description
Bourns® Model EMS22 is a non-contacting rotary
magnetic encoder with a Hall Effect application-
specific standard product (ASSP) capable of
producing four distinct output waveforms. These
waveforms include 2-bit quadrature up to 256 PPR*,
Step/Direction up to 512 PPR, Pulse-Width
Modulated (PWM) output with 1024 positions, and
Absolute with 1024 positions.
Model EMS22 is available in both a 3.3 and 5.0 Vdc
supply voltage and is offered in two different
versions. This product has the capability of rotating
up to 10,000 RPM while maintaining code accuracy,
making it suitable for MMI applications such as
industrial automation. This performance is achieved
by utilizing dual ball bearings in the construction of
the device, resulting in extended rotational life up to
100,000,000 shaft revolutions (beyond 100,000,000
shaft revolutions in some configurations).
This model is produced and assembled utilizing
state-of-the art production equipment along with
lean principles to provide our customers with a high
performance product at a competitive price.
The EMS22 non-contacting encoder is ideal for
use in harsh environments where extreme levels of
temperature, moisture and particles are present. The
outstanding performance of this device is attributed
to the non-contacting technology and superior
performance of the austriamicrosystems® AS5040
Hall Effect ASSP. In addition, this product is sealed
to IP** 65 with an optional upgrade to IP 67.
The EMS22 is RoHS compliant in accordance with
Directive 2002/95/EC of the European Parliament
and Council of 27 Jan 2003 on the restriction of the
use of certain hazardous substances in electrical and
electronic equipment.
* 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
most common among all contacting and non-
contacting encoders. Quadrature, also known as
2-bit quadrature or incremental, is often used to
determine magnitude (count) and direction (up/
down) by an external interface circuit. EMS22
comes equipped with such capability; an external
interface circuit is not required. It also offers an
indexed output with an adjustable width of one or
three times the absolute position value that can be
used for counting the shaft rotation.
Absolute:
Absolute output refers to the absolute
angular position. This type of output is especially
useful for applications where the absolute position
of a device, such as a camera, is necessary to locate
an object. Also with 1024 distinct angular positions,
the EMS22 offers very high resolution indexing at
every 0.35 °. This type of output code is not affected
by a power outage to the encoder since each angular
position of the encoder has a unique code.
PWM:
Pulse-Width Modulation is another form
of absolute waveform that utilizes the square wave
output generated by the sensor to control the
duty cycle of the output at different desired shaft
positions. The EMS22 encoder can generate pulse
widths as low as 1 µs, and as high as 1024 µs in a
complete signal period of 1025 µs. Some advantages
of using this output waveform over other output
types include immunity to noise and faster data
acquisition.
Direction/Step:
This output is very similar to the
quadrature waveform but offers up to 512 PPR, as
opposed to 256 PPR in quadrature. This output can
be used in incremental counting applications where
a better resolution is desired. Indexing output is also
available with a Direction/Step output waveform.
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
environmental conditions such as mud, dust, grease,
oil, water and dirt, giving this product an edge in
performance over traditional optical and contacting
encoders. Figure 4 illustrates examples of harsh
environments.
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,
The designer and end user can expect cycle
life performance without degradation of signal
accuracy, a clear advantage over encoders that use
optical or contacting technology.
the EMS22 can have more than 50 times the life
expectancy of traditional contacting encoders.
Figure 4: Examples of Harsh Environments
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