Hall effect sensor
A Hall sensor (also Hall probe or Hall sensors, according to Edwin Hall ) utilizes the Hall effect to measure magnetic fields.
Operation
A simple Hall sensor through which a current flows and placed in a magnetic field perpendicular to it, it provides an output voltage that is proportional to the product of magnetic field strength and current ( Hall effect). Moreover, the signal is dependent on the temperature and may have an offset.
A Hall sensor also provides a signal when the magnetic field in which it is located, is constant. This is a decisive advantage compared to a sensor that is composed of the magnet and the coil. Once this pair and the magnetic coil to one another does not move, the induced voltage is zero in the coil and the magnet is not detected.
Types
In analog Hall-effect sensors of the current is controlled and the temperature dependence of the signal, the offset, as well as noticeable non-linearities are compensated. The quality of this compensation (and the Eichbarkeit of the overall system ) determine the suitability and quality of the Hall sensor as a measurement device for magnetic flux.
Digital Hall sensors, the signal of an analogue Hall sensor is transformed by a comparator to a digital signal.
Designs
Hall sensors are made of thin semiconductor die, because in them the charge carrier density thus the electron velocity is small and large, to maximize the Hall voltage. Typical designs are:
- Rectangular shape
- Butterfly shape
- Cross shape
Most of these Hall elements are integrated in circuits in which signal amplification and temperature compensation is performed.
Applications
- Measuring the magnetic field (magnetic flux density )
- Potential-free current measurement ( current sensor ): If the magnetic field generated by a current-carrying conductor or a coil, you can measure the current floating in this conductor or coil.
- Non-contact and non-contact signal generator
- Coating Thickness Gauges
- Commutation electronically commutated motors
Or for position sensing.
In the automotive industry, see Hall sensors variety of applications, eg in the buckle, as wheel speed sensors, the door locking system in the pedal state detection in the transmission circuit or for detecting the ignition timing. Main advantage is the insensitivity ( non-magnetic ) dirt and water. In the power plant technology Hall sensors are used for example to detect the turbine speed.
Furthermore, they are found in brushless motors, for example, in PC cooling fans and disk drives.
There are also computer keyboards with Hall sensors under each key.
Hall sensors with analog signal outputs are used for the measurement of very weak magnetic fields ( geomagnetic field ), for example, used as a compass in navigation systems.
As current sensors are used in the gap of the iron core of a traversed by the measuring current coil or conductor. These current sensors are available as a complete assembly, are very fast, can be used in contrast to current transformers and to measure DC currents and provide electrical isolation between the most connected to the mains power circuits and the control electronics.
As position detection sensors or contactless switch, they work in conjunction with permanent magnets and have integrated a threshold switch.
Hall effect sensors may be used in conjunction with an excitation coil and a receiver coil in place in metal.
Spinning current Hall sensor
In order to suppress the resulting geometry by mistake, piezoresistive effects, inhomogeneous temperatures etc. offset voltage, Hall sensors are designed with multiple ports (usually 8). Two of these ports are used as a power supply, two as Hall voltage pickup. This method is used primarily for integrated sensors application and uses the periodicity of the piezoresistive constants in the chip level. The functions of the ports are in turn reversed. By appropriate evaluation of the measurement results, the offset voltage is significantly reduced.
Specifications
Sensitivity is usually specified in millivolts per gauss (mV / G). The following applies:
In addition, look for mV / VT, mV / AT, mV / mA mT etc. use. It refers to the Versorgungs-/Testspannung or current in the indication for the sensitivity with one.