Detailed Interpretation of 5 Misunderstandings Regarding Hall Sensors

The Hall effect sensor is generally used for proximity inspection, linear offset detection and rotary encoder in automotive and industrial systems. At present, contemporary applications have high requirements for system characteristics. IC manufacturers must release high sensitivity, integrate more functions, expand available sensing directions and reduce power consumption - this will help expand the application range of Hall effect sensor to the next few decades.

This article explores various common misconceptions about Hall utility sensors and their practical applications.

Myth 1: Hall utility sensors only provide simple switch information

Many electromechanical designs require the use of sensors to detect objects, which provide a simple logical signal to indicate their existence. One example is that when opening and closing the laptop cover, the Hall sensor can recognize and decide when to turn on or off the power. Another example is aggression in door and window sensors. Once the internal magnetic threshold is exceeded, these applications typically use a simple Hall utility switch, which will convert its voltage. Although these Hall utility switches are very useful, they are not the only common types of Hall utility sensors - lockers and linear devices. Compared to switches, latches primarily used for rotating numbers only convert their outputs when there is an opposite magnetic field as previously experienced. For accurate displacement measurement, a linear Hall effect sensor is required, because it can define objects with high resolution, and the information provided by the sensor position far exceeds the switch information. Figure 1 reflects the transfer function of each sensor.

Figure 1: Hall utility switches (a) and (b), latches (c), and linear sensors (d) and (e) derive responses.

Myth 2: Hall effect sensor is difficult to achieve low-power solution

Although some Hall utility sensors do consume current within the milliampere range and are not suitable for battery power supply, there are also other Hall utility switches that are suitable for low sampling rates (5 Hz or lower, reducing the average current to below 1 µ A. In order to achieve low power consumption, these devices cycle between high-power activity measurement and extremely low-power sleep. Because the duration of the active state is much shorter than the sleep interval (ts), So the total average current consumption is very low (refer to Figure 2).

Figure 2: Power consumption timing chart.

Myth 3: The working range of Hall utility sensors is very limited

Because the magnetic field decays Exponential decay with the distance, some people think that the Hall effect sensor has no good practical application range. However, the Hall effect sensor with high sensitivity can detect useful magnetic fields from a distance. Taking DRV5032 as an example. Table 1 shows the front induction spacing for all equipment combinations using small low-cost ferrite magnets (12) mm x 12 mm x 6 mm). The lowest sensitivity DRV5032ZE can detect magnets ranging from 4.0 mm to 7.5 mm, while the detection range of DRV5032FA is between 18.7 mm and 44.6 mm. If a more sturdy and identical grade 52 NdFeB magnet is used, the detection distance will increase by nearly 3 feet.

Table 1: Frontal induction spacing of two DRV5032 Hall utilization switch combinations.

Myth 4: Hall effect sensors have at least three wires

Most Hall effect sensor on the market have only three pins - VCC (power supply), output and GND (ground) - so it is generally believed that the three wires must be connected to the sensor. As shown in Figure 3a, remote connections can be achieved with only two wires for drain lead, voltage output, and three pin Hall utility switches. When a magnetic field is sensed, the device will generate current output through the GND pin. If the magnetic field is not detected, the device's output will not generate any current, therefore it will not generate output current based on the GND pin. Please note that the idea of determining resistance requires an analog-to-digital converter (which can be integrated into a microprocessor) and an external resistor. But this will affect the invalid voltage level.

To reduce or eliminate signal distortion, reliable transmission data must be exported. TMAG5124 only requires power current and grounding to operate a dual pin solution. Figure 3b shows how to transmit low frequency or high level currents (both within the milliampere range) through the GND pin of the application.

Figure 3: Hall utility switch export application voltage (a) and current export TMAG5124 (b) two wire remote sensing.

Myth 5: When using Hall effect sensors, the placement of magnets is not sensitive.

Compared to sensors, the position of a magnet depends on many elements - some are system level elements, while others are inherent in the sensor itself. The external system elements for placing magnets are usually the magnet specifications, magnet material types, and operating temperature range. The larger the magnetic field, the greater the magnetic field. Among the most commonly used magnets, neodymium iron boron (NdFeB) magnetic field produces the strongest magnetic field, so its size is generally smaller. Heat removal is also important when selecting magnets, as it usually lowers the magnetic field.

Sensitivity level and sensing direction (inside and outside the plane) are important factors that affect the placement of specific magnets in sensors, as well as the quantity and configurability of packaged goods and onboard sensors. The Hall effect sensor has a higher sensitivity and can detect magnets farther away. Most Hall sensors use switches and lockers to detect magnetic fields perpendicular to the packaging surface, but some can detect the horizontal direction of the packaging. TMAG5123 is a good example, when vertical placement is inconvenient, the horizontal placement design will bring more mechanical flexibility. Another example is the application of a two-dimensional dual channel lock, which can monitor multiple axes; They can be placed in almost all positions related to magnets.

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