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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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