Ultrasonic detection, infrared detection, grounding loop detection, video detection, radio frequency detection, etc. The working principle of ultrasonic parking detector is to measure the measured distance through the reflection of the measured object and the time difference after receiving the echo. It is a non-contact measuring instrument. Mainly used in parking guidance system, it has many characteristics, such as comparing the measured distance data with the preset number, and outputting the on-off switch signal if it reaches the preset value. The receive circuit receives that ultrasonic echo signal reflect by the object, and the chip includes pre-amplification, amplitude limiting amplification and shaping, so that the single chip compute whether the echo data is correct or not and the time difference, and calculates the distance value of ranging. When installing and debugging, it is forbidden to touch the surface of ultrasonic probe with hands or other objects to avoid signal lag and damage. When ranging, the distance between the rangefinder and the measured object should be kept constant, and the measured object should be centered as much as possible to make the measured distance reading accurate.

Detector is an important part of parking space guidance system. Using the working principle of ultrasonic ranging, it collects real-time parking space data of parking lot, controls the display of parking space indicator light, and transmits parking space information to node controller in time through 485 network. The detector consists of a detector main body and a detector bracket. The main devices on the detector body include ultrasonic probe, stop light connecting wire, power supply, 485 network connecting wire, detection distance setting jumper, 485 communication indicator lamp and stop information indicator lamp. Based on the working principle of ultrasonic ranging, the measured distance is measured by non-contact measuring instrument by using the time difference after ultrasonic emission, reflection of the measured object and echo reception. The use of advanced ultrasonic detection methods will not cause the problem of false alarm caused by the change or interference of the external environment, like the use of infrared and microwave detection methods. The alarm distance can be set flexibly. When the vehicle is in place and the measured distance is less than the preset distance, an LED light signal is generated, and the vehicle arrival information is sent to the controller through the RS-485 interface.