Unlike resistive current sensors, Hall effects current sensors generate an output voltage that is proportional to the current flowing in the conductor. The output voltage is then processed by a detection block. This block can have a simple amplification stage or a more complicated circuit to eliminate any Hall device drift error. This is because Hall devices generate a potential voltage, which is proportional to the core magnetic field. This potential voltage is then amplified by a transformer. The transformer can also be a low-cost device, but this is limited to alternating currents. When it comes to current monitoring, hall effect sensors provide a high level of current stability and sensitivity. These devices are based on the principle of the Hall effect, which involves the generation of a magnetic field by the current flowing in the conductor. These devices have two types: anomalous and ordinary. The anomalous type has two important properties: a small pole pitch and an initial rapid change in the Hall constant. However, these properties can be limited by the device's air gap, which reduces the efficiency of the core in converting the primary current into a strong magnetic field. The air gap can also lead to a phenomenon known as the fringing flux. The fringing flux phenomenon is illustrated in Figure 2. In this case, the flux lines do not follow a straight path and deviate from it. This leads to a negative offset in the Hall sensor output voltage. Hall effects are also susceptible to EMI. The EMI caused by conducted and radiated electromagnetic fields can dramatically influence their performance. Several tests were carried out to identify the effects of EMI on Hall affect current sensors. These tests included direct power injection (DPI) tests and Bulk Current Injection (BCI) tests. These tests were performed with various configurations and a variety of frequencies. The results showed that there was an EMI-induced offset voltage at 500 kHz and a maximum induced offset voltage of approximately 1.25 GHz. These figures indicate that EMI current sense resistor manufacturer was a major factor in the performance of Hall affect current sensors. In addition, there was also an induced offset voltage at the higher frequencies, which was not measured in this study. This offset voltage was measured for an incident RF power of 34 dBm. However, the magnitude of this offset was only about a tenth of the magnitude of the induced offset voltage. The induced offset is a function of the size of the air gap and the magnitude of the Hall magnetic field, which are both determined by the current flowing in the conductor. However, there are also non-ideal effects, such as the coercivity of the core, which can affect the measurement accuracy of open-loop current sensing. The detection block of a Hall effect current sensor also has a non-inverting gain stage and a hysteresis comparator. These components are located a few millimeters behind the surface of the chip's housing. You can get more enlightened on this topic by reading here: https://en.wikipedia.org/wiki/Shunt_(electrical).
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