KMT31

Magnetic Field Sensors Angle Sensor KMT 31 Function principle Magnetoresistive materials can change their resistivity in an external magnetic field. The variation of the resistivity is determined by the rotation of magnetisation with respect to the direction of the current flow. Permalloy (Ni81Fe19) is commercially used as magnetoresistive material. The relative change of resistivity is 2-3 % for this material. The high sensitive and small size sensor consists of a silicon chip coated with thin film permalloy stripes. These stripes form a Wheatstone bridge whose output voltage depends on the magnetic field. Characteristic Magnetic fields vertical to the chip surface have no influence on the output voltage. A strong magnetic field Hrot ≥ 50 kA/m parallel to the chip surface causes a sinusoidal output signal which is determined by the angle between field direction and orientation of the permalloy stripes of the Wheatstone bridge. The field Hrot is created by a permanent magnet which rotates over the sensor. The sensor output gives information about the direction of the magnet. The output characteristic of an additional galvanic seperated Wheatstone bridge is 45° phase shifted compared with the other bridge. Vmax1 Bridge 1 0,8 Bridge 2 0,6 0,4 0,2 0 0 -0,2 Output voltage of both Wheatstone bridges versus angle α of the magnetic field direction -0,4 -0,6 -0,8 Vmin1 0° 45° 90° 135° 180° 225° 270° 315° 360° [ ] Application The KMT 31 allows the contactless counting of the revolutions of a rotating magnet which is mounted on the axis of a wheel. Zero output voltages of the Wheatstone bridges are used as trigger signals. The sense of rotation of the wheel is taken into account by comparing the signal outputs of both Wheatstone bridges which are proportional to sin2(α) or sin2(α + 45° The angle can be determined by evaluating these signals. ). Alternatively it is possible to use the voltage signals of four half bridges which are trimmed on Vb/2. Sensors in thin film technology HL-Planartechnik GmbH Hauert 13, D - 44 227 Dortmund, Tel.: +49 (0) 231/97400, Fax.: +49 (0) 231/974020 Internet: http://www.hlplanar.com E-Mail: service@hlplanar.de Magnetic Field Sensors Angle Sensor KMT 31 Technical data Absolute maximum ratings Parameter Supply voltage Total power dissipation Operating temperature range Storage temperature range Sensor chip alignment error Symbol VB Pto Tamb Tstg Unit V mW ° C ° C ° Value 5 120 -40 ... + 125 -65 ... +125 ≤2 αe Electrical characteristics (Tamb= 25° Hrot ≥ 25 kA/m) C, Parameter Bridge resistance Offset voltage Half bridge symmetry Sensitivity Output voltage range Zero offset angle hysteresis Symbol RB VOFF /VB (Vs/2 - Vo)/VB Sα (|Vmax|+ |Vmin|) /VB Unit kOhm mV/V mV/V (mV/V)/° mV/V ° Value 3 ± 1.0 ≤ ± 2.0 ≤ ± 2.0 > 0.418 ≥ 24 ≤1 Condition bridge 2 bridge 1 α=0° α=0° α=0° α=45° α=45° α=45° ∆α Parameter Temperature coefficients ( - 25 ° < Tamb < 125 ° C C) of bridge 1 and 2 Symbol TCBR TCSV TCSI TCOFF Unit %/K %/K %/K (µV/V)/K Value 0.30 ± 0.05 -0.30 ± 0.05 0.00 ± 0.05 ≤±3 Bridge resistance Open circuit sensitivity (VB = const) (IB = const) Offset voltage Housing of KMT31: SM-8 bridge 1: pin 4: + VB pin 8: GND pin 1: - V0 pin 5: + V0 bridge 2: pin 3: + VB pin 7: GND pin 2: - V0 pin 6: + V0 (GND) (+ VB ) (+ V0 ) (- V0 ) (GND) (+VB ) (+ V0 ) (- V0 ) Assembly is pining independent. Sensor mirror symmetrically built ! Sensors in thin film technology HL-Planartechnik GmbH Hauert 13, D - 44 227 Dortmund, Tel.: +49 (0) 231/97400, Fax.: +49 (0) 231/974020 Internet: http://www.hlplanar.com E-Mail: service@hlplanar.de 21.05.03, Zn