霍尔效应在传感器应用培训

Type of permanent magnets
The main types of materials are as follow name AlNiCo Ferrites SmCo NdFeB material Aluminium Nickel Cobalt Strontium Ferrite Samarium Cobalt Neodynium Iron Born
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TT AES
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Applications Unipolar
Unipolar Hall-effect sensor ICs, often referred to as Hall effect switches, operate using only a positive magnetic field. A single south pole magnet, with sufficient magnetic strength (flux density) greater than the IC's operate point (BOP), will cause the device to switch to its on state. Once on, the unipolar IC will remain on until the magnetic field is reduced to below the IC's release point (BRP). When the magnetic field reaches BRP, or flux densities less than BRP, the unipolar IC will switch off
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Technology Permanent magnet
Remanence (Br) BH max
Coercivity (Hc)
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Technology Hall Effect IC
What is a Hall Effect IC?
A back bias magnet application is an application where the magnet is at the back of the IC (non branded face)
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Applications Latch
Latching Hall-effect sensor ICs, often referred to as "latches," are digital output Hall-effect switches that latch output states. Latches switch on with a positive magnetic field and switch off with a negative magnetic field. Because these sensor ICs latch on and latch off, the application must present both north and south magnetic fields for proper operation.
2) Demagnetisation Curve
This is the absolute performance of any magnetic material
The Main points are:
A - Remanence (Br) Remanence is the remaining magnetisation when the applied field to magnetise the magnet is removed. This is measured in Gauss or Tesla – In this case 12kG B - Coercivity (bHc – Normal Coercivity, jHc – Intrinsic Coercivity) Normal coercivity is the applied field required to reduce the external field generated by the magnet to zero. Intrinsic coercivity is the applied field required to fully demagnetise the material. This is measured in Oersteds or kA/m2 In this case: bHc = 10.8 kOe & jHc = 14 kOe C – Bhmax It is the maximum energy stored within the magnet. This is measured in MGOe or kJ/m In this case 33MGO
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Technology Permanent Magnets
How is a magnet's magnetic performance measured
1) Flux or Gauss meter
Using a Hall effect probe - a measurement of magnetic flux density in a given position. Suppliers or users do not usually quote this.
Hall Effect and magnets
Technology and applications
Bertrand Plancon
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1. Technology
1. 2. 3. 4. Hall Effect Principle Permanent Magnets Hall Effect IC Front & back bias
Table 1. Bipolar Switch Magnetic Characteristics Characteristic Operate Point Release Point Hysteresis Symbol BOP BRP Bhys Min. – –95 30 Typ. 32 –20 52 Max. 95 – – Unit G G G
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Technology Hall Effect IC
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Technology Front & back bias magnet
A front bias magnet application is an application where the magnet is in front of the IC (branded face)
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Applications Latch
–| BOP | Magnetic operate point, at which a positive magnetic field of sufficient strength, | +B | > | BOP |, switches the device on (output low). –| BRP | Magnetic release point, at which a negative magnetic field of sufficient strength, | B | > | BRP |, switches the device off (output high). –| BHYS | Magnetic switchpoint hysteresis. BHYS = | BOP | + | BRP |. Hysteresis is designed into every Halleffect switching device.
It is a device that converts a magnetic field value into a electrical output signal. It is composed of a Hall Plate, an amplifier and a circuitry.
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2. Applications
1. 2. 3. 4. Latch Unipolar Bipolar Rotary
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Technology Hall Effect Principles
A voltage develops across a current-carrying conductive plate when a magnetic field is applied perpendicular to plate
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Applications Bipolar
From this specification we can see that this sensor IC operates between 95 and –95 G and that hysteresis is typically 52 G. We can also see that the typical switchpoints are not symmetrical, basically to optimize manufacturing yields. In fact, if the operate point of the device is towards the high end of the specification, say 80 G, the hysteresis will still typically be 52 G (hysteresis remains very consistent for a particular sensor IC design) therefore, the release point will be about 28 G. This sensor IC has unipolar characteristics. The other sensor IC that can squeeze into the distribution is the notorious negative switch. If the release point approaches its minimum value the sensor IC will be what is called a "negative switch." If BRP is for example 80 G, the hysteresis will still typically be 52 G; therefore, the operate point will be about 28 G. A negative switch is still a unipolar sensor IC.