A rangefinder is a dead reckoning instrument used to measure the distance to a target and perform dead reckoning. There are many forms of rangefinders, usually a long cylinder, composed of an objective lens, an eyepiece, and a rangefinder knob, used to measure the target distance.
The rangefinder is an instrument used for distance measurement, designed according to the principles of optics, acoustics and electromagnetic waves.
Classification of rangefinder：
Rangefinders can be divided into the following three categories from the basic principle of distance measurement:
1. Laser range finder
The laser range finder is an instrument that uses laser to accurately measure the distance of the target. When the laser range finder is working, it emits a very thin laser beam to the target, and the photoelectric element receives the laser beam reflected by the target. The timer measures the time from the launch to the reception of the laser beam, and calculates the distance from the observer to the target.
Laser range finder is currently the most widely used range finder, and laser range finder can be classified into handheld laser range finder (measurement distance 0-300 meters), telescope laser range finder (measurement distance 500-20000 meters) . At present, the mainstream of the market is laser rangefinder. The top two brands of handheld laser rangefinder in the world are Leica and Bosch. The telescope laser rangefinder is a long-distance laser rangefinder. It is widely used outdoors. Telescope The top four brands of laser range finders in the world are Tuyad, Phonen, Alfa and Nikon.
2. Ultrasonic distance meter
The ultrasonic range finder measures according to the characteristics of ultrasonic waves reflected back when encountering obstacles. The ultrasonic transmitter emits ultrasonic waves in a certain direction, and starts timing at the same time as the emission. The ultrasonic waves propagate in the air, and return immediately when encountering obstacles on the way, and the ultrasonic receiver immediately interrupts and stops timing when it receives the reflected wave. By continuously detecting the echo reflected by the obstacle after the generated wave is emitted, the time difference T between the emitted ultrasonic wave and the received echo is measured, and then the distance is calculated. Ultrasonic range finder, because the ultrasonic wave is greatly affected by the surrounding environment, so the general measurement distance is relatively short, and the measurement accuracy is relatively low
3. Infrared range finder
An instrument that uses modulated infrared light for precise distance measurement, and the measurement range is generally 1-5 kilometers. The non-diffusion principle of infrared rays is used: because infrared rays have a small refractive index when passing through other substances, long-distance rangefinders will consider infrared rays, and the propagation of infrared rays takes time. When infrared rays are sent from the rangefinder when encountering a reflective object, it is reflected back and received by the rangefinder, and then the distance can be calculated according to the time from sending out to being received by the infrared ray and the propagation speed of the infrared ray
The advantages of infrared ranging are cheap, easy to manufacture, and safe. The disadvantages are low accuracy, short distance, and poor directionality.
how to choose a rangefinder? What parameters to look at?
Look at the material
The material may be ignored by many people, because the essence of the rangefinder is that we still measure the distance, and the quality of the material may not be that important. But the material we care about should meet our daily construction site use, and it doesn't matter if it is a brittle plastic.
The purpose of buying a rangefinder is to measure distance, and the smaller the error, the better. If the measurement accuracy is ±2mm, it means that the error is plus or minus 2mm. The general laser range finder will carry a distance, which indicates the test accuracy within a certain range.
This must be seen, some rangefinders use dry batteries, and some are rechargeable. Generally, it is the battery, because the rangefinder cannot be turned on frequently, and it will not be turned off for a long time.
Actual Use Scene
From the point of view of use, if it is a project, you may need to buy professional ones. Old brands are better, such as Bosch, Dongcheng, Delixi, etc.; if it is for your own family use, you can buy some fashion brands, such as The Duke laser rangefinder recommended by Xiaomi Youpin, which looks good, but it is not suitable for engineering.
In terms of indoor and outdoor, theoretically speaking, it is best to use the green line for outdoor.
The sharpness is mainly reflected in two aspects. One is the clearness of the screen itself. You can’t buy a rangefinder and find that the words are blurred when you use it for the first time. Well, if it is used in engineering, it is inevitable that there will be bumps and bumps. If you can't touch it a little, it will break. These two points need attention.
Sometimes during construction, it is inevitable to encounter bad weather, so it cannot be put in the pocket, and if it is a little wet, it cannot be used. Good rangefinders generally don't have this problem.