The principle of parking lot vehicle detector and ground sense coil

The principle of parking lot vehicle detector and ground sense coil

1. Working principle

The ground induction coil vehicle detector is a vehicle detector based on the principle of electromagnetic induction. It usually embeds a toroidal coil under the road subgrade of the same lane, and passes a certain working current as a sensor. When the vehicle passes through the coil or stops on the coil, the iron on the vehicle itself will change the magnetic flux in the coil, causing the change of the coil loop inductance. The detector judges the passing vehicle status by detecting the change in the inductance. . There are generally two detection methods for inductance change: one is to use a phase latch and a phase comparator to detect the phase change; the other is to use a coupling circuit composed of a loop coil to detect its oscillation frequency.

2. System composition

The ground-sensing vehicle detector includes a ground-sensing coil and a detector. The coil is used for data acquisition, and the detector is used to realize data judgment and output corresponding logic signals. The detector is generally composed of a rack, a central processing unit, a detection card and a terminal block.

The central processing unit is a module that calculates the collected signals, and is generally a single-board computer with an embedded operating system, with strong digital computing, storage capabilities and communication interfaces. By scanning the port, the change time of the level is captured to calculate the corresponding traffic data

When the detection vehicle passes through or is stationary in the detection area of the induction coil, the inductance of the induction coil will decrease. The function of the detection card is to detect this change and output the corresponding level accurately. When detecting high-speed passing vehicles, there may be inaccurate detection of vehicle length and vehicle speed, and the sensitivity of the detector needs to be adjusted correctly. The current vehicle detectors generally have the function of multi-level sensitivity adjustment.

 停车场车辆检测器和地感线圈的原理

    1、 工作原理

    地感线圈车辆检测器，是一种基于电磁感应原理的车辆检测器。它通常在同一车道的道路路基下埋设环形线圈，通以一定工作电流，作为传感器。当车辆通过该线圈或者停在该线圈上时，车辆本身上的铁质将会改变线圈内的磁通，引起线圈回路电感量的变化，检测器通过检测该电感量的变化来判断通行车辆状态。电感变化量的检测方法一般有两种：一种是利用相位锁存器和相位比较器，对相位的变化进行检测；另一种是利用环形线圈构成的耦合电路对其振荡频率进行检测。

 

    2、 系统组成

    地感车辆检测器包括地感线圈和检测器，线圈作为数据采集，检测器用于实现数据判断，并输出相应逻辑信号。检测器一般由机架、中央处理器、检测卡和接线端子组成。

    中央处理器是对采集信号进行计算的模块，一般是一个带嵌入式操作系统的单板机，具备较强的数字计算、存储能力和通讯接口。通过对端口的扫描，捕捉电平的变化时间，以此计算出相应的交通数据

    检测车辆通过或静止在感应线圈的检测域时，通过感应线圈的电感量会降低，检测卡的功能就是检测这一变化并精确地输出相应的电平。在对高速通过车辆进行检测时，可能会存在车长、车速检测不准确的情况，需要正确调节检测器的灵敏度。目前的车辆检测器一般都具有多级灵敏度可调的功能。