What Is a Velocimeter?

A speedometer is an instrument used to measure the speed of a vehicle. There are two commonly used speedometers: radar speedometer and laser speedometer. Among them, the speed measurement principle of the radar speedometer is the Doppler effect; the speed measurement principle of the laser speedometer is laser ranging.

Chinese name: Speedometer
Foreign name: Measure Speed Instrument

Suitable for: vehicle
Types of: Radar speedometer, laser speedometer
Function: Measure vehicle speed

Speedometer type

Commonly used speedometers are mainly divided into radar speedometers and laser speedometers.

Radar speedometer

Laser Doppler Velocimeter

Speedometer radar speedometer

The main principle of radar velocimeter is the Doppler Effect, that is, when the target approaches the radar antenna, the frequency of the reflected signal will be higher than the frequency of the transmitter; otherwise, when the target moves away from the antenna, the frequency of the reflected signal will be low. To the transmitter frequency. Radar speedometers emit electromagnetic waves that are reflected back when they touch an object. When the touching object has a displacement movement toward or from the back, there is a frequency difference between the electromagnetic wave emitted from the speedometer and the reflected electromagnetic wave. The frequency difference is used to obtain the speed of the object's movement and achieve the purpose of speed measurement. It has been widely used in police speed testing and other industries. There are two types of radar speedometers: fixed and portable. ^[1]

Speedometer fixed speedometer

Fixed speedometers are, as the name implies, speed measurement instruments that measure in a fixed position. Refers to the method of speed measurement by fixing the vehicle speedometer on a pole frame, a gantry frame or a speed box, and it is often used on highways.

Fixed speed meter

Speedometer Portable Speedometer

A portable speedometer refers to an instrument that can be moved flexibly and can be held by hand, mounted on a tripod, or mounted on a vehicle to perform speed measurement. Because of its flexibility, it is applied to radial speed measurement in various industries.

Portable speedometer

The difference between the speedometer

Functional difference

Fixed speedometers are mainly used by relevant enforcement departments for overspeed fines on vehicles. This type of speedometer is generally equipped with a camera function. By combining radar with a camera, the radar triggers the camera to take a snapshot of the speeding vehicle for evidence of punishment . In addition, there is a type of fixed speedometer (vehicle speed prompt screen) with a display screen, which is placed on the roadside, and displays information about passing vehicles, their speed values, and whether they are overspeeding.

The functions of portable speedometers are relatively diversified. There are simple speedometers. For example, purely for speed measurement, you only need to know the speed of the object, and do not need to make any records or punishment. There are also full-featured ones, such as speedometers with output interfaces, with printing, and with snapping.

The difference in the occupation of human resources

General fixed speedometers are all-weather automatic speed measurement systems. There is no need for on-duty operations, and automatic speed measurement, snapping, uploading and other functions can greatly reduce human resources. The portable mobile speedometer, whether it is a handheld or traffic police, requires relevant personnel to be on duty.

Difference in price and application range

Fixed speedometers take into account installation, commissioning, and uploading image information to the Internet. Fixed speedometers with the same configuration are generally more expensive than portable speedometers. Fixed speedometers are generally used on highways, national roads, provincial roads and other fast and prone road accidents. And the application range of portable speedometer is relatively more extensive, including some factories, mines, airports, docks and other large factories, there are also mobile speedometers (such as mobile electronic police) for traffic police.

Laser Speed Velocimeter

The laser velocimeter uses the principle of laser ranging. Laser ranging (that is, electromagnetic waves with a speed of 300,000 km / s) is to determine the distance between the measured object and the test point by transmitting a laser beam to the measured object and receiving the reflected wave of the laser beam and recording the time difference. . The laser velocimeter performs laser distance measurement on the measured object twice with a specific time interval, and obtains the moving distance of the measured object during the time period, thereby obtaining the moving speed of the measured object. ^[2]

Speedometer Features

The laser velocimeter has the following characteristics:

The speed measurement distance is far longer than the effective range of radar speed measurement, and it can measure a distance of 1000 meters;

High speed measurement accuracy, the error is less than 1000 meters / hour;

Because laser speed measurement is measured by laser reflection, if the measured vehicle is far away and is in a moving state, it will lead to a low success rate and difficulty of laser speed measurement;

Can only be applied in a stationary state;

The ability to obtain evidence is far greater than the radar speedometer, so it is widely recognized and promoted worldwide.

Aiming at the shortcomings of laser velocimeters, laser doppler velocimeters have emerged, which have the advantages of non-contact measurement, high accuracy, small measuring points, fast dynamic response, measurable multi-dimensional speed, and discrimination of speed direction.

Speedometer application

There is a new type of laser velocimeter called the laser velocimetry and forensic system, which includes a laser speed detector and a camera that measures the speed of the vehicle. When in use, the speedometer performs a speed test on each passing vehicle. Once the speedometer finds a speeding vehicle, it will automatically take an image of the offending vehicle and record the time and target speed. It is a new type of traffic management law enforcement tool, which provides a reliable technical evidence collection method for managing illegal speeding.