According to different principles, it can be divided into mechanical sensors and electronic sensors.

Hall sensor is the most widely used, and its working principle is: under the action of magnetic field, a transverse potential difference is generated on a metal plate with current.

This voltage is proportional to the magnetic field and the control current:

VH=K╳|H╳IC|

Where VH is the Hall voltage, H is the magnetic field, ic is the control current, and K is the Hall coefficient.

Hall effect is more obvious in semiconductors than in metals, so Hall elements are generally made of semiconductor materials.

Using Hall element, non-contact current measurement can be carried out. As we all know, when current passes through a long straight wire, a magnetic field will be generated around the wire. The magnitude of the magnetic field is proportional to the current flowing through the wire. This magnetic field can be collected by soft magnetic materials and then detected by Hall elements. Because the magnetic field has a good linear relationship with the output of the Hall element, the signal measured by the Hall element can directly reflect the current, that is, I∞B∞VH.

Where I is the current passing through the wire, B is the magnetic field generated by the current passing through the wire, and VH is the Hall voltage generated by the Hall element in the magnetic field B, which can be expressed as an equation when the appropriate proportional coefficient is selected. Hall sensor is made according to this working principle.

At present, the radar speed sensor is used on the expressway, and I am not very clear about the specific working principle. Hall sensor is almost the most widely used sensor in industry.