Detection by Hall sensors
Pin identification

    The Hall sensor has 3 or 4 pins externally. For the Hall sensor with 3 pins, they are respectively the power terminal, the ground terminal and the signal output terminal. For the Hall sensor with four pins, they are the power terminal, the ground terminal and two signal output terminals respectively. Hall sensors with three pins are more commonly used. The pins of Hall sensors can be identified by their shape, as shown in Figure 10-5 specifically. The surface of a Hall sensor marked with text is usually the magnetic-sensitive surface, and the sensitivity is high when it is directly facing the N or S magnetic poles.
    The resistance values between each pin of the U18 switch-type sensor measured by the Rx1k range of the MF-47 pointer multimeter are shown in Table 10-1.

    The resistance values between pins 1 and 2 and 3 of the U18 switch-type Hall sensor were measured using an MF-47 pointer multimeter, and are shown in Figures 10-6 and 10-7.

2. Quality detection
    The schematic diagram of the Hall sensor's quality detection is shown in Figure 10-8. Connect a 5V power supply between the power pin and the ground pin of the sensor. Then, use a multimeter to set the DC voltage to the 2.5V range. Connect the red and black test leads to the output pin and the ground respectively. Bring a piece of iron close to the magnetic sensitive surface of the Hall sensor. If the Hall sensor is normal, there should be a voltage output. The pointer of the multimeter will swing. The greater the swing of the pointer, the higher the sensitivity of the sensor. If the hands of the watch do not move, the Hall sensor is damaged.

    The measurement of the U18 switch-type R sensor using the BM9205 digital multimeter and the MF-47 pointer multimeter is shown in Figure 10-9.

【 Knowledge Tips 】
    The type of Hall sensor can also be determined by the methods shown in Figures 10-8 and 10-9. If the output voltage changes slowly and continuously as the magnet approaches or moves away from the sensor, it is a linear Hall sensor. If the output voltage suddenly switches between high and low levels at a certain point, it is a switch-type Hall sensor.