Advantages and disadvantages of Hall effect sensors - Weikewei - Free user manual included
The performance characteristics of various Hall effect sensors are different, so it is difficult to accurately summarize the advantages and disadvantages of Hall effect sensors compared to other commonly used current sensing technologies, that is, inserting a precision resistor in the current path and then measuring the resulting voltage drop with differential amplification. However, in general, the value of Hall effect sensors lies in their non-invasive nature and providing electrical isolation between the current path and the measurement circuit. These devices are considered non-invasive because there are not many resistors inserted into the current path, so the tested circuit behaves almost as if there were no sensors. Another advantage is that the sensor consumes minimal power; This is particularly important when measuring high currents.
Regarding accuracy, currently available Hall effect sensors can achieve output errors as low as 1%. A well-designed resistive current detection circuit can exceed this value, but in high current/high voltage applications where Hall effect devices are particularly suitable, a 1% current detection circuit is usually sufficient.The disadvantages of Hall effect sensors include limited frequency range and high cost. ACS712 provides an internal bandwidth of 80 kHz, while Melexis MLX91208, sold as a "broadband" device, specifies a maximum of 250 kHz. On the other hand, a resistive current detection circuit with a high-speed amplifier can work well in the megahertz range. Meanwhile, as discussed above, the Hall effect itself is limited in measuring small currents.
One of the main advantages of Hall effect sensors is electrical isolation, which is commonly referred to as electrical isolation in circuit or system design. Whenever a design requires two circuits to communicate in a way that prevents any direct current flow, the principle of electrical isolation is included. A simple example is when a digital signal passes through an optical isolator, which converts voltage pulses into optical pulses, thereby transmitting data in an optical rather than electrical manner. One of the main reasons for implementing electrical isolation is to prevent issues related to the ground circuit:The basic circuit design principles assume that interconnected components share a common ground node, which is assumed to be at 0 volts. However, in real life, the "grounding node" is composed of conductors with non-zero resistance, which act as a loop for current to flow back from the circuit to the power source. Ohm's Law reminds us that current and resistance generate voltage, and the voltage drop in a circuit means that the "ground" potential of one part of the circuit or system is different from that of another part. These differences in ground potential can lead to problems ranging from insignificant to catastrophic.
By preventing direct current from flowing between two circuits, electrical isolation enables circuits with different ground potentials to communicate successfully. This is particularly relevant for current sensing applications: low-voltage sensors and processing circuits may need to monitor large, highly variable currents, such as motor drive circuits. These large, rapidly changing currents will result in significant voltage fluctuations in the return path. Hall effect sensors allow the system to monitor driving currents and protect high-precision sensor circuits from these harmful ground fluctuations.