How to choose a rangefinder?

The principle of operation of the ultrasonic rangefinder

Ultrasonic rangefinder is the easiest-to-use device for measuring distance. Its design consists of the following elements:

• Sound wave transmitter.
• Sound wave receiver.
• A microprocessor.
• Display.

The principle of operation of the ultrasonic transmitter

The principle of operation of the device is as follows: the ultrasonic transmitter sends a pulse towards the object. Reflecting from the object, the signal is sent to the receiver, which in turn transports the wave to the microprocessor (computer). The time it takes for the wave to return to the receiver determines the distance to the object. Usually the device is equipped with a liquid crystal or LED display, such as TOPEX 31C902 , so all data is displayed on it. In many models, the following phrase can be read in the description: "the presence of a laser". However, this is not a full-fledged laser rangefinder, but just an indicator (pointer) projecting a beam to the place where the sound wave will be sent. The class of the laser beam in many sound models has a value of 2, which is quite enough for working indoors and in dim weather outside.

Pros and cons of ultrasonic rangefinders

The advantages of using ultrasonic tape measures are:

• Low price. A rangefinder with an error of only 0.5 percent can be purchased at a price of $ 25 to $ 70.
• Ease of use. There are several keys on the device body that are responsible for turning on the device, starting the wave and adding/subtracting measurements. Even a beginner can figure it out.

Of the disadvantages of using ultrasonic devices , the following can be noted:

• The influence of the environment. The accuracy of determining the distance directly depends on the density of the air and the moisture content in it. The higher the density, the longer the sound wave will pass through space, which means that the data obtained will be very inaccurate. Because of this, it is not recommended to use the device in wet weather outside.
• The range of work. The range of ultrasonic devices does not exceed 20 metres, which is why measuring the area of large building plots is not possible.

The principle of operation of the laser rangefinder

A laser device, or, as it is also called, a laser tape measure, is more versatile than ultrasonic, and is used for serious construction and installation work, to measure distances for laying water and sewer pipes, as well as to determine the size of some elements of furniture structures. The principle of operation of this device is similar to ultrasound: a laser pulse is transmitted from the active element in two directions, which is reflected from the object, returns to the receiver. For accurate measurement, it is necessary to press one side against the reference point (for example, a wall). The time spent on the passage of the distance allows you to calculate it with an accuracy of a millimetre.

Pros and cons of laser rangefinders

The laser rangefinder has the following advantages:

• Measurement accuracy. The device is able to determine the distance, area or volume with an accuracy of one millimetre, which is very important, for example, when combining two water or sewer pipes and other mounting elements.
• Measuring range. Depending on the measured object, you can purchase a device with a range of 20 to 300 metres.
• Stability. The device works stably in hot or cold weather. Also, it is not affected by the density of the air, as ultrasonic.

Of the minuses, it is worth noting the high price, which starts from 40 and can reach $ 2,000, depending on the additional features of the model.

General criteria for the selection of rangefinders

The selection of ultrasonic and laser tape measures is carried out according to the following criteria:

• Measuring range. In many cases, this is a key parameter that determines the choice in favor of a particular device. It is best to take a little with a margin from the estimated size of the site. For example, if a plot or room is less than 20 metres in size, it is better to take a device with a range of 30 metres, since it may be necessary to measure the diagonals. For household purposes, such as installing furniture or installing a boiler, the smallest laser tape measure is suitable. In rare cases, they acquire rangefinders with a range of more than 100 metres, which are more industrial than domestic. They are used for engineering and geological surveys, when it is necessary to measure large areas and with different landscapes. To work with them, you will additionally need a tripod.
• Measurement accuracy. Under equal favorable environmental conditions (for example, indoors or outdoors in sunny warm weather), ultrasonic devices have an error in measurements from 3 to 5 mm, and laser devices from 1 to 3 mm. These indicators are indicated in the product passport. However, it is worth noting that in adverse weather, the accuracy of ultrasound can drop significantly, increasing the error, but laser ones do not suffer from such a "disease". For household work, such as hanging a bookshelf, measurement accuracy is not very important, so you can buy an inexpensive tape measure, but when laying sewer pipes, when the slope should be perfectly accurate (7 cm for every 10 m), you need an accurate device.
• Automatic shutdown. On many (but not all) the devices have an automatic shutdown function. It is necessary to turn off the power in case the user forgets to do it himself. The time of automatic shutdown in different devices varies from 6 to 8 minutes of inactivity.
• Warranty service. Well-known brands provide a guarantee for their goods from 2 to 3 years. Pay attention to this detail when buying a rangefinder, since professional models are not cheap, and it is very problematic to fix it at home.

Additional features of laser roulette that are worth paying attention to

Unlike ultrasonic analogues, laser devices can have a lot of additional useful functions that determine their usefulness and cost:

• Memory. Thanks to the built-in memory, the device can remember the last measurement data. Some models can remember up to 30 numbers. This allows you to save all measurements, for example in the manufacture of furniture, and then use them during assembly. It also allows you to set certain values that are constantly required during calculations. This function eliminates the need to constantly enter them into the device.
• Wireless data transmission. Some models are equipped with Bluetooth to transmit information to a smartphone or laptop. If you are preparing some kind of installation project, then all the data can be immediately saved to the computer. It is also convenient for BTI employees when it is necessary to take measurements of several apartments at once per day. All information on each individual apartment is sorted on a PC.
• Volume and area metre. These functions allow you to measure the volume of any room or tank, as well as calculate the area of the site, being at one point. Volume measurement is useful when selecting heating equipment for a specific room, as well as when installing a septic tank (a tank for a drain pit).
• Optical sight. The design resembles a rifle sight, necessary for the visualization of a laser spot. The sight is usually equipped with expensive rangefinders with a range of over 200 metres. It is not necessary to buy a device with a sight for measurements inside small rooms, since the laser will be clearly visible to the naked eye.
• Pythagorean measurement. This function allows you to calculate the height of the building by the hypotenuse. That is, being at some distance from the building with a tripod, you can measure the height of the building without coming close to it.

Pythagorean Measurements

• Folding bracket (heel). This structural element allows measurements to be made from corners and door frames. Such a bracket has two positions: 90 and 180 degrees.

Folding bracket rangefinder (heel)

• Triangle function. It is necessary to obtain the area of a polygonal room. The user visually divides the room into triangles, and the rangefinder calculates each of them. Then the sum of the triangles is added and the finished result is obtained, as shown in the figure below.

Triangle Measurement

• Continuous measurement. With this function, the device is able to output data in real time. For example, a person needs to move the rack exactly 60 centimeters from the wall, which is easy to do by running a continuous measurement.