第六章磁敏材料及器件霍尔-磁阻英.pptx

二、二、The application of Hall sensor1.Hall micro displacement sensor Hall element has the advantages of simple structure,small size,good dynamic characteristics and long life.It is not only used to measure the magnetic flux density,active power and energy parameters,but also widely used in the displacement measurement.Fig.7-12 shows the number of work principle schematic of Hall displacement sensors.Fig.(a)is two identical magnetic field strength permanent magnets,the same polarity placing opposite,the Hall element being in the middle of two magnets.二、二、The application of Hall sensor1.Hall micro displacement sensorBecause the magnetic induction intensity in the middle of the magnet is B=0,the Hall potential UH output from Hall element is also zero.Then the displacement is x=0.If the Hall element has a relative displacement in the two magnets,the magnetic flux density of the Hall element also will change.Then the UH is not zero,which size will reflect the relative position changes between the Hall element and the magnet.This structure sensor has the dynamic range up to 5 mm,and the resolution is 0.001 mm.UHKxHall elementHall elementHall elementFig.7-12 The working principle of Hall displacement sensor Fig.(b)shows a simple structure Hall displacement sensor,which is a sensor consist of a permanent magnet magnetic circuit.When x=0,the Hall voltage is not zero.Fig.(c)is a Hall displacement sensor composed of two same structure magnetic circuits.In order to obtain a better linear distribution,the magnetic pole end is with the pole shoe.Adjusting the initial position of the Hall elements,Hall voltage is UH=0.This sensor has a high sensitivity,but the detecting amount of displacement is small.It is suitable for measuring micro-displacement and vibration.2.2.Hall rotate speed Hall rotate speed sensorsensor Fig.7-13 is several different structure Hall rotate speed sensors.The input shaft and the measured shaft of magnetic wheel are connected.When the measured shaft is rotating,the magnetic wheel is rotating therewith.The Hall sensor which is fixed near the magnetic wheel can generate a corresponding pulse by the time each of the small magnet passing.Measuring the number of pulses per unit of time,the measured speed will be obtained.The The number number of of the the small small magnet magnet on on the the magnetic magnetic wheel wheel determines determines rotate rotate speed speed measurement measurement resolution resolution of the sensor.of the sensor.1-Input shaft;2-Rotary table;3-magnet;4-Hall sensorFig.7-13 several structures of Hall rotate speed sensor3.Hall Counting Assembly Hall switch sensor SL3501 is an integrated Hall element which has a high sensitivity.It can feel a small magnetic field change.Thus,it can be used to count the measured black metal parts.Fig.7-14 is a work schematic diagram and circuit diagram of counting ball.When the steel ball passes the Hall switch sensor,the sensor will output pulse voltage of peak 20mV.After the voltage magnifies through the operational amplifier A(A741),the semiconductor triode VT(2N5812)is driven to work.The output of VT can be connected to the counter for counting,and the measured value is displayed by the displayer.steel ballinsulating plateHall switch sensormagnetcounterFig.7-14 work schematic and circuit of Hall count devicesBroken Wire DetectionHall-effect Broken Wire Detection Devicesteel wire ropeHall elementpermanent magnetamplificationsmoothingcomputerbroken wires signalstocks wave signal Crack Detection of Ferromagnetic MaterialsNSCurrent Sensor When current flows through the wire,a magnetic field will be generated around the wire.The size of the magnetic field is proportional to the current flowing through the wire.The magnetic field can be gathered by soft magnetic materialssoft magnetic materials,then using Hall device for detection.leakage DC Hall sensorDS-50LT series Hall switch integration sensor is a kind of magneto-dependent sensor which is combined the Hall effect with integrated circuit technology.It can perceive everything quantity related to the magnetic information and output it in the form of switch signal.Hall switch integration sensor has the advantages of long service life,non-contact wear,no spark interference,no conversion jitter,high working frequency,good temperature characteristics and adapting to the harsh environment and so on.Hall Switch Integration Sensor It is consist of the voltage regulator circuit,the Hall element,amplifier,waveshaping circuit and open-circuit output,five parts.Voltage regulator circuit allows the sensor to work in a wide range of supply voltages;open-circuit output allows the sensor to be easily interfaces with a variety of logic circuits.1)Structure and working principle of Hall switch integration sensordiagram of Hall switch integration sensor inside structure23putput+stabilivoltVCC1Hall elementamplificationBTreshapinggroundH 3020ToutputVoutR=2k+12V123（b）application circuit （a）exteriorexterior and application circuit of Hall switch integration sensor1232)Performance Curve of Hall Switch Integration Sensor As can be seen from the performance curve,the operating characteristic has a certain characteristic hysteresis BH.The reliability of the switch action is very good.BOP in the figure is the magnetic induction intensity of working point open,and BRP is magnetic induction intensity of the release point off.Performance Curve of Hall Switch Integration SensorVOUT/V12ONOFFBRPBOPBHBTechnical Parameters of Hall Switch Integration Sensor：working voltage、magnetic induction intensity、output cut-off voltage、output current flow、operating temperature、operating point.0 The curve shows the relationship between the applied magnetic field and the sensor output level.When the applied magnetic induction intensity is higher than BOP,the output level is from high to low,and the sensor is in the ON state.When the applied magnetic induction intensity is lower than BOP,the output level is from low to high,and the sensor is in the OFF state.3)the application of Hall switch integration sensor （1）interface circuit of Hall switch integration sensorGeneral interface circuit of Hall switch integration sensorHall Displacement SensorHall Displacement Sensor Hall displacement sensor can be made into the structure as shown in Fig.(a).A Hall element is placed in the interval between the two opposite polarity and same magnetic field intensity magnetic steels.When the control current I is constant,Hall electric potential UH is proportional to the external magnetic induction intensity.If the magnetic field is within a certain range,the change gradient dB/dx in the x-direction as shown in Fig.(b),is a constant.When the Hall element is moved in the x direction,the change of Hall electric potential should be a constant K(the output sensitivity of the displacement sensor):That is UHKx.It suggests that the Hall electric potential is in a linear relationship with displacement.The polarity of output potential reflects the direction of the element displacement.The higher the magnetic field gradient,the greater the sensitivity.the more uniform magnetic field gradient,the better the output linearity.When x0,component is placed in the center of the magnetic field,UH0.This displacement sensor can generally be used to measure tiny displacement of 12mm.It has the characteristics of small inertia,fast response,non-contact measurement.This principle can be used to measure some non-electricity physical quantity,such as force,pressure,acceleration,liquid level and differential pressure and so on.(a)structure(b)Magnetic field changeFig.9-23 Hall displacement sensor二、二、Automobile Hall IgniterAutomobile Hall Igniter The above figure is a schematic diagram of the Hall electronic igniter structure.The Hall element(Fig.3)is fixed on the platinum city of the automobile distributor.A magnetic isolation cover 1 is assembled in the points in the fire.According to the number of automobile engine cylinder,the vertical side of cover leaves evenly spaced gap 2.When the gap is alignment on the Hall element,flux through by Hall element forms a closed loop circuit.So the circuit is breakover,as shown in the above Fig.(a).the Hall circuit outputs low level(less than or equal to 0.4V).When the bulge part of cover side blocks between the Hall element and the magnets,the circuit is cut-off,as shown in the above Fig.(b).Hall circuit outputs high level.The principle of Hall electronic igniter is shown below.When the Hall sensor outputs low level,BG1 cut-off,BG2 and BG3 conduction,a constant current will pass the ignition coil primary.When the Hall sensor outputs high level,BG1 conduction,BG2 and BG3 cut-off,the primary current of the igniter is cut-off.In this case,the energy stored in the ignition coil will output as the high pressure discharge form in the secondary lines,namely the discharge ignition.Automobile Hall electronic igniter has the advantage of non-contact,fuel-prudent,applying to wicked working environment and all kinds of speed,good kaltstartverhalten.At present it has been widely used abroad.Fig.9-24 Schematic of Hall sensor magnetic circuit1-Magnetic isolation cover 2-gap of magnetic isolation cover 3-Hall element 4-magnetic steel Fig.9-25 schematic of Hall electron igniter1-distributor with Hall sensor 2-swutch amplifier 3-ignition coil1.Magnetic Resistance Magnetic Resistance is a magneto element based on the magnetoresistive effect,also called MR element.The application range of magnetoresistor is wide.It can be used to make magnetic field detector,the displacement and angle detector,the ammeter and the magnetic susceptibility AC amplifier and so on.一、一、Magnetoresistive Effect If the metal for passing a current or the slice of semiconductor material is applied a external magnetic field vertically or horizontally to the current,its resistance value will increase.Called this phenomenon magnetic resistance effect,magnetoresistance effect for short.Under the applied magnetic field,the Lorentz force of some carrier is larger than the Hall electric field force,so its trajectory is towards the direction of the Lorentz force.The path of these carriers flowing from one electrode to another electrode is longer than that when no magnetic field,thus,the resistivity increasing.When at a constant temperature,within the magnetic field,the magnetic resistance is in direct proportion to the square of magnetic induction intensity B.If the device is only in simple cases,electronic involved in conducting,theoretical derivation for the magnetic resistance effect equations asWhere,B the specific resistance when the magnetic induction intensity is B;0 the specific resistance when the magnetic induction intensity is 0;electronic mobility;B the magnetic induction intensity.When the change of the specific resistance is B 0,the relative change of the specific resistance is:Therefore,when a constant magnetic field,the higher the electron mobility of the material(such as InSb,NiSb and InAs semiconductor materials),the more obvious magnetic resistance effect.When there is only a kind of carrier in materials,magnetoresistive effect almost can be ignored.The Hall effect is more strongly.If the electrons and holes are both in the materials(such as InSb),the magnetoresistive effect is very strong.Magnetoresistive effect is also closely related to the shape and size of the magnetic resistor.The magnetoresistive effect related to the size and shape of the magnetic resistance effectmagnetic susceptibility and resistance is called the geometric magnetoresistance effect of magnetoresistive effect.If considering the influence of the shape,the relationship between the relative change of resistivity,magnetic induction intensity and migration rate can be expressed as Rectangle magnetic resistance device is only in the conditions of L(length)b(width),it only showes a higher sensitivity.L1).Because the electron movement towards a side,it will inevitably produce Hall effect.When Hall electric field EH forces on electron fE an electric field force is balance to the magnetic field forces on electron a Lorentz force fL,electron trajectory will no longer continue to offset.So in the middle of chip,electron movement direction is parallel with the direction of length l,only both ends are tilted.In this situation,the electron motion path increases no significantly,resistance increases not much,too.LbBBGeometric Magnetoresistance EffectII（a）（b）Figure(b)is many parallel evenly spaced metal strips(that is,the short-circuit grid)put on Lb rectangle magnetic resistance materials.With short circuit Hall electric potential,this grid magnetic resistance device is shown in figure(b).It is equivalent to many flat strip magnetic resistance in series.So grid magnetic resistance devices increase resistance under zero magnetic field,also improve the sensitivity of magnetic resistance devices.Experimental results show that,for InSb materials,when B=1T,resistance can be increased 10 times(Because there is no time to form a larger Hall electric field EH).One is on a longer element piece used by vacuum coating method,as shown in figure(a),many short circuit electrode(grating)components.The other is eutectic type semiconductor(when drawn InSb single crystal,adding 1%Ni,it can be obtained InSb and NiSb eutectic material)magnetoresistor made up of InSb and NiSb.In this eutectic,NiSb is a acicular crystal in a certain orientation.It has good electrical conductivity.The diameter of pin is in 1m or so,length approximately 100m.Many of this pins are side-to-side setup,which instead of the effect of metal strip short circuit Hall voltage.Because of the low temperature properties of InSb,it often adds some N type tellurium or selenium to the material,forming doped eutectic.But the sensitivity will be to lose a little.Magnetoresistor is made of a direction to precipitation of metal in the crystallization process,as shown in the above figure(b).Besides,there is also disc-shaped.There is each an electrode in the center and on the edge,as shown in the above figure(c).Magnetoresistor is mostly made into disk structure.二、二、The structure of Magnetoresistor Magnetoresistor often is used two ways to make:(a)short circuit electrode (c)disk structure(b)precipitated metal directional in the crystals Fig.9-9 the structure of magnetoresistor Various Various shapes shapes of of magnetoresistor,magnetoresistor,the the relationship relationship between between the the magnetic magnetic resistance resistance and and magnetic magnetic induction induction intensity intensity is is shown shown in in the the right right figure.figure.Seeing Seeing from from the the figure,figure,the the magnetic magnetic resistance resistance of of the the disc disc shaped shaped sample is the largest.sample is the largest.The The sensitivity sensitivity of of magnetoresistor magnetoresistor is is generally generally non-linear,non-linear,and and greatly greatly influenced influence