AS5311 Magnet Specification Magnetic Multipole Strip MS10-300 Pole Length 1.0mm, 300 Poles 1 General This specification defines the dimensional and magnetic properties of a multipole magnetic strip for use with the AS5311 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 1.00 1 Pole Length Deviation Amplitude Variation Number of Poles Resolution Max mm Bpk Magnetic Field Temperature Drift TkBr www.austrimaicrosystems.com Results in pole pair length of 2.0mm (300 poles @ 1.0mm) % of 2*Lp Measured at Bz=0, active area ±10 % of Bpk All poles within active area 1.95 poles µm 0.488 Magnetic Field Amplitude @ 0.8mm Distance Note 1.5 300 Res Unit Revision 0.1 Excluding poles with L<L P at the ends of the strip AS5311 @ 10-bit incremental output AS5311 @ 12-bit absolute serial output mT -0.2 all poles within Vertical component of the magnetic field strength in the center of the strip at 25°C %/K 1-7 AS5311 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 MS10-300 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 is 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 AS5311 Linear Multipole Magnetic Strip Magnet Specification 4 Magnet Dimensions MS10-300 Strip Dimensions 10 W = 10 Bpk Bpk Figure 1: 1 2 3 4 5 6 7 8 9 10 N S N S N S N S N S 297 298 299 300 S N S N recommended scanning path T = 1.0 L =2 L = 300 Alignment of Magnet Strip and Sensor IC When aligning the magnet strip to the AS5311 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 0.3 +- 0.2mm. Note that the vertical distance depends on the strength of the magnet. The AS5311 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 AS5311. The vertical distance should be set such that the magnetic field is in the “green” range. See the AS5311 datasheet for more details. See also Figure 3 for measurement data of the MS10-300 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 AS5311 has a length of 2.0mm, hence the total stroke is Stroke = Length of active area – length of Hal array = 300mm – 2.0mm = 298mm www.austrimaicrosystems.com Revision 0.1 3-7 AS5311 Linear Multipole Magnetic Strip Magnet Specification Figure 2: Alignment of Magnet Strip with AS5311 Sensor IC position value increases leftmost magnet position Die C/L S N S N S N S N S N 3.0475±0.235 AS5311 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 AS5311 Linear Multipole Magnetic Strip Magnet Specification 5 Measurement Data Figure 3 and Figure 4 show typical test results of MS10-300 samples. Note that austriamicrosystems AG does not guarantee this data for all magnet samples. Please contact the magnet supplier for detailed specifications. Automatic Gain Control Figure 3 shows a typical measurement result using the MS10-300 magnetic strip at three different vertical gaps between strip and IC surface: 200µm, 400µm and 600µm. The AGC automatically adjusts for fluctuating magnetic field strength. Note that a stronger magnetic field (shorter airgap) results in a smaller AGC value. The vertical gap should be adjusted such that the AGC is within its regulation limits (>0….<255). Figure 3: AS5311 AGC Values versus Airgap AGC M S10-300 250 Z= 600µ 200 AGC 150 Z= 400µ 100 Z= 200µ 50 0 2000 3000 4000 5000 6000 7000 8000 9000 10000 X [um] Accuracy (non-linearity) of the MS10-300 Magnetic Strip Figure 4 shows the accuracy of an MS10-300 sample over the full stroke range of 8mm at three different vertical gaps. The graphs show that the accuracy is virtually identical (about +/- 10µm) for all three airgaps due to the automatic gain control of the AS5311. Note: the accuracy depends greatly on the length of each pole and hence from the precision of the tool used for magnetization. Figure 4: Integral nonlinearity versus Airgap INL MS10-300 40 30 INL = 200 Error [um] 20 10 0 -10 INL = 400 INL = 600 -20 -30 -40 2000 3000 4000 5000 6000 7000 8000 9000 10000 X [um] www.austrimaicrosystems.com Revision 0.1 5-7 AS5311 Linear Multipole Magnetic Strip Magnet Specification 6 Adhesive Tape Specification www.austrimaicrosystems.com Revision 0.1 6-7 AS5311 Linear Multipole Magnetic Strip Magnet Specification Copyrights Copyright © 2011, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. 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Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life sustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystems AG rendering of technical or other services. 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