Basic principle: Based on the electromagnetic induction principle, when the magnetic flux of the magnetic field where the N-turn coil is located changes, the induced potential E =-D φ/dt in the coil changes. Therefore, when n magnetic bars are embedded in the turntable, the induced potential of the coil changes every n times, and the rotation speed can be measured by the circuit of amplification, shaping and counting.

According to the principle of magnetoelectric sensor, the end face of magnetoelectric sensor is about 2mm away from the rotating disk, and the center of magnetoelectric sensor is aligned with the center of magnetic steel.

One type of speed sensor is divided into PNP and NPN. Specific wiring and installation as shown in figure 7-6.

Figure 7-6 Wiring Diagram

When the NPN sensor is connected to the tachometer, pay attention to the DIP setting of the tachometer, as shown in Figure 7-7.

The setting of the scanning rate parameter of the tachometer will affect the final display result, as shown in Figure 7-8.