AS5304 Magnet Specification Magnetic Multipole Strip MS20-150 Pole Length 2.0mm, 150 Poles 1 General This specification defines the dimensional and magnetic properties of a multipole magnetic strip for use with the AS5304 magnetic linear motion and off-axis rotary angle encoder. Material: Strontium ferrite bonded 2 Dimensional Specification Parameter Symbol Min Typ Max Unit Note Strip Length L 300±2 mm Active length = 300mm Strip Width W 10±0.2 mm Active width = 10mm Strip Thickness T 1,3±0, 15 mm 1mm rubber bonded magnet on 0.3mm stainless steel strip Thermal Expansion Density Delivery -6 17 x10 /K Mechanical length expansion 3.5 3.65 3.8 1.43 4.64 7.85 g/cm 3 magnetic rubber stainless steel Single cut pieces without adhesive, rolls of 25m, 50m (up to 100m max.) 3 Magnet Specification Parameter Pole Length Symbol Lp Min Typ 2.00 1 Pole Length Deviation Amplitude Variation Number of Poles Resolution Res Magnetic Field Amplitude @ 0.8mm Distance Bpk Magnetic Field Temperature Drift TkBr www.austrimaicrosystems.com Max Unit mm Note Results in pole pair length of 4.0mm (150 poles @ 1.0mm) 1.5 % of 2*Lp Measured at Bz=0, active area all poles within ±10 % of Bpk All poles within active area Excluding poles with L<L P at the ends of the strip 150 poles 25 µm AS5304 @ incremental output mT Vertical component of the magnetic field strength in the center of the strip at 25°C -0.2 Revision 0.1 %/K 1-7 AS53xx Linear Multipole Magnetic Strip Magnet Specification Parameter Symbol Min Typ Max Unit Note depending on accuracy grade 40 20 Cumulative error standard µm/m 10 A20 A10 Thermal Expansion Temperature Range Tamb -40 25 1E-4 1/K Mechanical length expansion 100 °C scale mounted, no bending Magnetization The MS20-150 magnet strip is magnetized on the top side and bonded on a steel support with elastomer adhesive (bottom). Note that the polarization of the magnet will change when it is rotated as the pole arrangement not symmetric. This will influence the position of the index pulse. An index pulse is generated when the North and South poles are placed over the Hall array as shown in Figure 2. The incremental output count increases when the magnet is moving to the left, facing the chip with pin#1 at the lower left corner (see Figure 2, top drawing). At the same time, the absolute position information increases. Likewise, the position information decreases when the magnet is moved in the opposite direction. Note that there is no hysteresis at the absolute output. In order to get a stable 12-bit absolute reading, it may be necessary to filter the values by averaging, e.g. a moving average calculation in the external microcontroller. Averaging 4 readings results in 6dB (=50%) noise and jitter reduction. An average of 16 readings reduces the jitter by a factor of 4. Mounting the Magnet Strip The magnet strip may be mounted directly on magnetic or non-magnetic surfaces. When magnetic surfaces are used, the strip must be mounted on top of the surface, but not immersed in a cavity, as this may weaken the magnetic field of the magnet. When mounting the magnet on a non-magnetic surface, either method is acceptable. For more rigid demands, magnet suppliers offer customized solutions where the magnet material is directly overmolded on the carrier, e.g. a shaft, bushing, plate, etc.. Please contact your magnet supplier for more information. A list of recommended suppliers is available for download on the austriamicrosystems website. www.austrimaicrosystems.com Revision 0.1 2-7 4 Magnet Dimensions MS20-150 strip dimensions 10 W = 10 Bpk Bpk Figure 1: 1 2 3 4 5 6 149 150 N S N S N S N S recommended scanning path T=2 L=4 L = 300 Alignment of Magnet Strip and Sensor IC When aligning the magnet strip to the AS5304 sensor IC, the centerline of the magnet strip should be placed exactly over the Hall array. See Figure 2 for the position of the Hall array relative to Pin #1. Vertical Distance The vertical distance between the magnet strip and the top of the IC package should be ≤ 0.8mm. Note that the vertical distance depends on the strength of the magnet. The AS5304 automatically adjusts for fluctuating magnet strength by using an automatic gain control (AGC). There are several indicators for proper magnetic field strength available with the AS5304. The vertical distance should be set such that the AO voltage is between 1.0 and 4.0V. See the AS5304 datasheet for more details. See also Error! Reference source not found. for measurement data of the MS20-150 magnetic strip. Lateral Stroke The lateral movement range (stroke) can cover the active area of the magnetic strip (see Figure 1) as long as all Hall sensors of the IC are covered by the magnet. The Hall array on the AS5304 has a length of 2.0mm, hence the total stroke is Stroke = Length of active area – length of Hal array = 300.0mm – 2.0mm = 298.0mm www.austrimaicrosystems.com Revision 0.1 3-7 Figure 2: Alignment of magnet strip with AS5304 sensor IC position value increases leftmost magnet position Die C/L S N S N S N S N S 3.0475±0.235 N AS5304 Package Outline 1.00 position value decreases rightmost magnet position S 2.576±0.235 3.200±0.235 Die C/L N S N S N S N S N 1.00 3.0475±0.235 vertical airgap magnet strip carrier see text 1.00 ± 0.1 Note: all dimensions are in mm Note that the polarization of the magnet will be reversed when it is rotated or flipped (see Magnetization for more details). www.austrimaicrosystems.com Revision 0.1 4-7 AS53xx Linear Multipole Magnetic Strip Magnet Specification 5 Adhesive Tape Specification www.austrimaicrosystems.com Revision 0.1 5-7 Copyrights Copyright © 2011, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. 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Contact Information Headquarters austriamicrosystems AG A-8141 Schloss Premstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 Magnet Supplier Information Bogen Electronic GmbH1, Potsdamer Strasse 12-13 14163 Berlin Germany http://www.bogen-electronic.de/ For Sales Offices, Distributors and Representatives, please visit: www.austrimaicrosystems.com Revision 0.1 6-7 AS53xx Linear Multipole Magnetic Strip Magnet Specification http://www.austriamicrosystems.com/contact www.austrimaicrosystems.com Revision 0.1 7-7