Ultrasonic rangefinder working principle. Ultrasonic or laser rangefinder? Operating principle of ultrasonic rangefinder
Vasilyeva Maria 108
A thankless task such as measuring the distance between objects or walls in a room with a regular tape measure has long since become a thing of the past. Today, a modern device for accurate and fast non-contact distance measurement will help us with this - rangefinder . This device is used in construction and repair, geodesy, hunting, fishing, photography and comes in the following types: ultrasonic rangefinder and laser rangefinder.
Ultrasonic rangefinder like an echo sounder, it sends and picks up the reflection of directed beams of sound waves in the ultrasonic range (approximately 40 kHz), analyzes the time it takes for the sound to return, and from this data calculates the distance between distant objects. The disadvantages of these types of devices are: a short measurement distance of up to 35 meters, the object to reflect the sound signal must be quite large in size, ultrasound can be extinguished when passing obstacles in the form of fabric materials. However, ultrasonic rangefinders are more common because they are less expensive than laser rangefinders.
Laser rangefinder does not analyze the reflection time of the sound signal, but compares the phases of the sent and reflected light signals. The distance measurement accuracy of a laser rangefinder is higher than that of an ultrasonic rangefinder. The measurement error is very small - only 1–5 mm when the laser signal passes through curtains and carpets. The maximum measured distance can be up to 250 meters, but bright sunlight or rainy weather somewhat dims the brightness and clarity of the laser beam. And most importantly, the high cost of laser rangefinders compared to ultrasonic ones tips the balance when purchasing a measuring device in favor of the latter.
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viva-telecom.org | RUB 20,100 | |
| OptTools | 14,669.70 RUR | ||
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Bigham | RUB 11,645 | |
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viva-telecom.org | RUB 11,205 |
Considering the short measurement range and relative measurement accuracy, ultrasonic devices belong to the household class of rangefinders, while most laser models belong to professional rangefinders.
In addition to directly measuring the distance between objects, many rangefinders have a number of useful and necessary options, such as:
Calculation of the area and volume of the room;
Addition, subtraction, calculation of the area of a triangle, calculation using the Pythagorean formula and memorizing the results;
Display backlight, sound signal, automatic shutdown, measuring point marker, compass, thermometer, timer, built-in level, inclinometer, magnetic declination;
Installing the device on a tripod, on a folding bracket, on a wrist strap, or on a belt pouch;
Possibility of providing data to personal computer, Bluetooth support and so on.
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viva-telecom.org | RUB 12,500 | |
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I ordered this device because of my craving for multifunctional gadgets. A rangefinder, and even a tape measure for measuring short distances in one bottle - that’s cool! Of course, I was aware that measuring distances with ultrasound has many disadvantages and cannot be compared with measuring with a laser rangefinder, but the opportunity to test a new, and not yet described, device prevailed, and I ordered it.
So if you're wondering what happened...
The rangefinder came in standard OEM packaging for the store - a white cardboard box. The kit included the rangefinder itself, a power source (a rare 23A 12V battery in our region) and instructions. 
The rangefinder is similar in design and size to a regular tape measure. Only, unlike a roulette, there is a liquid crystal display and functional buttons on the side. 
On the opposite side there is a battery compartment and a button for folding the tape measure. Yes, here, unlike a regular tape measure, the tape is fixed when removed. 
On the front side there is an ultrasound emitter/receiver, a laser pointer and a measurement activation button. 
At the top there is a power switch and a tape measure output. The total length of the tape measure is 1 m. Material is plastic. On one side the scale is in millimeters, on the other - in inches. Compared to my 3-meter tape measure made of metal tape, it looks quite modest. 
The weight of the rangefinder with battery is almost 90 g. 
The body of the device is held together with only two bolts (the other two cover the compartment with the tape measure). This made it possible to open it without any problems in order to get acquainted with the internal structure. 
Measurements
Declared device parameters:Measuring distance: 0.5 – 18 m.
Accuracy: 0.5%
Operating frequency: 40 kHz
Operating temperature: 0 – +43 degrees Celsius
Unlike measurements with a tape measure, to carry out correct measurements with ultrasound, certain conditions must be met:
1) Since the measurement is carried out according to the principle of echolocation (the time during which the ultrasonic wave reaches an obstacle, is reflected from it and returns back is measured), it is necessary that the space between the device and the object, the distance to which is measured, be free. It is also undesirable to measure objects that can absorb sound waves (for example, curtains) and have an uneven surface.
2) The speed of propagation of ultrasound in air depends on temperature. To assess the temperature, a temperature sensor is built into the rangefinder. Since it is located inside the device, when transferring it from one temperature environment to another, before measuring, you should wait until the temperature of the device is equal to the ambient temperature.
3) The front of the sound wave expands as it propagates, so if the object to which the measurement is being made is located at a greater distance, it must also be large enough (that is, measuring the length of a narrow and long corridor may be incorrect).
4) Atmospheric fluctuations also affect the measurement, so it is not recommended to use the device outdoors.
The restrictions imposed on measurements, as you can see, are so significant that they exclude professional use this tool.
In everyday life, measurements are needed quite rarely; they usually take place in more comfortable conditions and do not require millimeter precision. Personally, I did them with a regular tape measure. The applicability of an ultrasonic rangefinder for household measurements, in my opinion, depended on how convenient and accurate it would be compared to a tape measure.
First of all, let's check the accuracy of temperature determination. I think it's acceptable. 
The measurement process consists of pointing the device at the surface to which the distance is being measured and pressing the “MEAS” button. The surface where the sound wave is applied is illuminated with a laser (this is so that we can see where exactly we are measuring the distance), a soft click is heard and the result is displayed on the screen. Everything takes a couple of seconds.
As for the accuracy of measurements. The rangefinder has the option of measuring distance from the trailing (default) or leading edge. Regardless of the choice of edge, for some reason the device adds 2 cm to the measurement result. Judging by a similar problem described in, this is obviously some kind of electronic nuance. The accuracy, as you can see, in both cases is comparable to the accuracy of a tape measure (naturally, taking into account the 2 cm indentation). The distance between the edges is 7cm.
From trailing edge 
From leading edge 
The measurements were carried out in a narrow and long corridor, precisely in conditions where the use of an ultrasonic rangefinder is not recommended. For this reason, the starting point of measurements was located approximately in the middle of the corridor, distances were measured on both sides of it, and the summation function was used to determine the total length (button " +/= ").
In one direction it turned out to be 5.29 m. 
To the other - 9.29 m. 
Total – 14.58 m. Total measurement time – 30 seconds. 
In principle, any number of distances can be summed up in this way; the main thing here is not to get lost in the measurement process.
The length of the corridor, as measured with a tape measure, was 15 m, and the process of measuring with a 3-meter tape took about 5 minutes (including pencil marks). This result is more accurate, but labor costs are significantly higher.
In addition to summation, the device can multiply values (button " x/="), which allows you to calculate the area 
And volume 
Conclusions
Regarding the use of an ultrasonic rangefinder as such:
Pros:Comfortable. No need to wander around the room with a tape measure. The measurement process takes just seconds.
Cons:
Low measurement accuracy. The process of sound transmission is influenced by quite a few external factors, so the measurement error in different conditions will also be different. In addition, if with a tape measure we can simply measure on the floor, regardless of its slope, then the rangefinder will have to be fixed at the level so that the wave does not go to the side.
Limited scope. Distances can only be measured to relatively large and flat objects and only indoors.
Regarding the very idea of combining a tape measure and a rangefinder.
As usual, the Chinese have a great idea and lame implementation. The ultrasonic rangefinder itself is in little demand due to low accuracy and limited scope. If you equip it with a tape measure, you can take quick measurements with a rangefinder, and more accurate or inaccessible to the rangefinder measurements with a tape measure.In reality, the scope of application of tape measurements is much higher, therefore, it would be necessary to quality roulette attach a range finder. That is, a rangefinder should be an additional option, rather than a mediocre tape measure turning a mediocre rangefinder into a multifunctional device.
In general, as an idea, such a “combine” has a right to life. As for this specific implementation, it's up to you. Personally, I satisfied my curiosity by receiving this tool for free for review from the online store Chinabuye.com. Would I buy it? I think not. There are too few situations in which I would find a use for it.
I'm planning to buy +9 Add to favorites I liked the review +9 +30Rangefinders, modern devices, are used to measure distances and are used in various branches of construction and in the manufacture of furniture. They owe their popularity to the highest accuracy and measurement range. Replacing a primitive tape measure, the rangefinder does an excellent job of taking measurements and gives more accurate results. When measuring large distances, its error is millimeters.
There are 2 types of this measuring device, but which rangefinder to choose (laser or ultrasonic) can be determined after studying technical characteristics and the qualities of each of the devices.
The simplest and cheapest device developed by modern designers is an ultrasonic rangefinder. A similar design is also called an echo sounder. They are quite often used in many household and industrial areas.
The design of the ultrasonic rangefinder includes a receiving and transmitting unit, as well as a microprocessor, which has a storage function and subsequently processes and displays the received information.
Operating principle of ultrasonic rangefinder
An ultrasonic rangefinder works by directing emitted sound at an object, which in turn reflects it. The rangefinder detects with the receiving unit. This ultrasound is not heard by others. The speed of sound directly depends on the density of the air, which contributes to a more accurate calculation of distance.
In the process of introducing new technologies and production capabilities, the designers achieved improvements in the design of the device. This made it possible to create a new device that more accurately directed the sound beam. An ultrasonic rangefinder with a laser pointer was created. Such a device significantly increased the accuracy of measurements and facilitated the work.
Today you can purchase an ultrasonic rangefinder at any retail outlets that sell measuring instruments.
This device has significant disadvantages. The main disadvantage is the accuracy of the measurement, since it is determined taking into account the environment in which the sound will propagate. Parameters and values (the main one is density) cannot be constant and have the ability to change during the period of work. An important drawback is the limitation of the length of measurements, since the distance limits are from 30 cm to 20 m.
In this regard, ultrasonic devices can be used in cases where precise measurements and measurements within acceptable limits are not required. In other cases, it is better to purchase a laser rangefinder, although it costs a little more, but has better technical characteristics.
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Laser rangefinder: features
Today, a laser rangefinder, or as it is called differently - a laser tape measure, is a necessary device for construction and finishing. It is used for both internal and external work.
This type of rangefinder is a small optical-electronic device for measuring distances. Today's manufacturers are pleased to offer a wide range of models with advanced functions that allow you to calculate the area, volume of a room, and measure objects located in inaccessible places, which are carried out using the Pythagorean theorem. In addition, during work, you can transfer data for processing to a PC and, depending on the modification of the device, perform other additional functions.
Many models are equipped with shockproof, dust- and moisture-proof housings, and therefore can be used under any working conditions.
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The principle of working with a laser rangefinder
When working with this modification, the device is installed on a flat plane and turned on.
After this, the device must be configured and generate a laser beam, which is red and directed to the required point. This point is reflected in the receiving unit, and the distance of the device to the object is recorded on a special display located in the rangefinder body.
According to the following principle: the device sends pulses to the target, which, in turn, reflects them, and the built-in microprocessor element determines the length, taking into account the time from the moment the pulse was sent until the reflection was received.
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Advantages of a rangefinder as opposed to a simple tape measure
The laser rangefinder is characterized by the following features:
- When taking measurements, you can do without outside help.
- Using a laser rangefinder, it becomes possible to measure objects with obstacles that cannot be measured with a conventional tape measure.
- The use of such rangefinders significantly reduces the work time and takes measurements more accurately.
- The visible laser beam is a guide, and therefore easier and more convenient to work with.
- Using a laser device, you can carry out other work without any problems, for example, installing window frames, window sills, or pouring a cement floor.
- Such devices are capable of measuring not only length, but area and volume.
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Before purchasing a rangefinder device, you need to decide on the upcoming work, that is, for what purpose it is needed. The more functions a device has, the more it will cost.
Points to consider before choosing:
- Classification.
Similar devices are:
- household;
- professional.
If the device is purchased for interior decoration of apartments, then a simple household device will be suitable for these purposes. If you have to work under more severe conditions and on complex construction sites, then you need to think about professional equipment. But the price of professional devices is much higher. It also happens that some household rangefinders may be equipped with additional functions.
- Measuring range.
Modern laser measuring instruments can have a beam range of up to 200 m. When purchasing devices with a maximum measurement range, you need to pay attention to the device for installing a tripod, since when taking measurements at long distances, you need to have a tripod. If the device is used for the construction of a country house or on small construction sites, it is enough to use a rangefinder with a range of up to 50 m.
- Rangefinder accuracy.
Basically, all laser rangefinders have measurement accuracy with an error of 1.5 to 2 mm, which solves problems in domestic and professional settings.
- Manufacturer.
The quality of rangefinders also directly depends on the manufacturer. The best companies producing rangefinders are considered to be BOSH and Stabila. As a rule, devices from European manufacturers are much more expensive than Chinese-made products, but the quality of Chinese ones is much inferior.
- Warranty service.
Any well-known company provides a warranty card for its equipment, granting the right to service. In normal cases, the warranty is given for 1-2 years for household laser devices and up to 3 years for professional equipment. When purchasing a rangefinder, you need to find out whether there is a center for servicing the equipment of a particular company.
- Design and ease of use.
When selecting a laser device, you need to hold it in your hands. It should be comfortable, light and not fall out of your hands. The smaller the dimensions of the device, the more convenient it is to use, since it can even be placed in a pocket. For ease of use of the rangefinder, many manufacturers equip its body with rubber parts.
- Functionality.
Rangefinder is a device for measuring the distance to an object. The rangefinder helps robots in different situations. A simple wheeled robot can use this device to detect obstacles. The flying drone uses a rangefinder to hover above the ground at a predetermined altitude. Using a rangefinder, you can even build a map of the room using a special SLAM algorithm.
1. Operating principle
This time we will analyze the operation of one of the most popular sensors - an ultrasonic (US) rangefinder. There are many different modifications of such devices, but they all work on the principle of measuring the travel time of reflected sound. That is, the sensor sends a sound signal in a given direction, then catches the reflected echo and calculates the flight time of the sound from the sensor to the obstacle and back.
From a school physics course we know that the speed of sound in a certain medium is constant, but depends on the density of the medium. Knowing the speed of sound in air and the flight time of sound to the target, we can calculate the distance traveled by sound using the formula: s = v*t where v is the speed of sound in m/s, and t is time in seconds. The speed of sound in air, by the way, is 340.29 m/s. To cope with its task, the rangefinder has two important design features. Firstly, in order for sound to be reflected well from obstacles, the sensor emits ultrasound with a frequency of 40 kHz. To do this, the sensor has a piezoceramic emitter that is capable of generating such high frequency sound. Secondly, the emitter is designed in such a way that the sound does not spread in all directions (as is the case with conventional speakers), but in a narrow direction. The figure shows the radiation pattern of a typical ultrasonic rangefinder. 
As can be seen in the diagram, the viewing angle of the simplest ultrasonic rangefinder is approximately 50-60 degrees. For a typical use case, where the sensor detects obstacles in front of it, this viewing angle is quite suitable. Ultrasound can even detect a chair leg, while a laser rangefinder, for example, may not notice it. If we decide to scan the surrounding space, rotating the rangefinder in a circle like a radar, the ultrasonic rangefinder will give us a very inaccurate and noisy picture. For such purposes, it is better to use a laser rangefinder. It is also worth noting two serious disadvantages of the ultrasonic rangefinder. The first is that surfaces with a porous structure absorb ultrasound well, and the sensor cannot measure the distance to them. For example, if we decide to measure the distance from a multicopter to the surface of a field with tall grass, we will most likely get very fuzzy data. The same problems await us when measuring the distance to a wall covered with foam rubber. The second disadvantage is related to the speed of the sound wave. This speed is not fast enough to make the measurement process more frequent. Let's say there is an obstacle in front of the robot at a distance of 4 meters. It takes as much as 24ms for the sound to travel back and forth. You should measure 7 times before installing an ultrasonic rangefinder on flying robots. 2. Ultrasonic rangefinder HC-SR04
In this tutorial we will work with the HC-SR04 sensor and the Arduino Uno controller. This popular rangefinder can measure distances from 1-2 cm to 4-6 meters. At the same time, the measurement accuracy is 0.5 - 1 cm. There are different versions the same HC-SR04. Some work better, others worse. You can distinguish them by the pattern of the board on the reverse side. The version that works well looks like this:
Here's a version that may fail: 
3. Connection HC-SR04
The HC-SR04 sensor has four outputs. In addition to ground (Gnd) and power (Vcc), there are also Trig and Echo. Both of these pins are digital, so we connect them to any pins of the Arduino Uno:| HC-SR04 | GND | VCC | Trig | Echo |
| Arduino Uno | GND | +5V | 3 | 2 |
Layout appearance
4. Program
So, let's try to order the sensor to send a probing ultrasonic pulse, and then record its return. Let's see what the timing diagram of the HC-SR04 looks like.
The diagram shows that to start measuring we need to generate at the output Trig positive pulse with a length of 10 μs. Following this, the sensor will release a series of 8 pulses and raise the level at the output Echo, switching to the mode of waiting for the reflected signal. Once the rangefinder senses that the sound has returned, it will complete a positive pulse on Echo. It turns out that we need to do only two things: create a pulse on Trig to start measuring, and measure the length of the pulse on Echo, so that we can then calculate the distance using a simple formula. Let's do it. int echoPin = 2; int trigPin = 3; void setup() ( Serial.begin (9600); pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); ) void loop() ( int duration, cm; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite (trigPin, HIGH); delayMicroseconds(10); duration = pulseIn(echoPin, HIGH); cm = duration.print(cm); (100) Function pulseIn measures the length of the positive pulse on the echoPin leg in microseconds. In the program, we record the flight time of the sound in the duration variable. As we found out earlier, we will need to multiply the time by the speed of sound: s = duration * v = duration * 340 m/s Convert the speed of sound from m/s to cm/μs: s = duration * 0.034 m/µs For convenience, we convert the decimal fraction to an ordinary fraction: s = duration * 1/29 = duration / 29 Now let’s remember that the sound traveled two required distances: to the target and back. Let's divide everything by 2: s = duration / 58 Now we know where the number 58 in the program came from! Load the program onto the Arduino Uno and open the serial port monitor. Let's now try to point the sensor at different objects and look at the calculated distance in the monitor. Quests
Now that we can calculate distance using a rangefinder, we will make several useful devices.- Construction rangefinder. The program measures the distance every 100ms using a rangefinder and displays the result on a symbolic LCD display. For convenience, the resulting device can be placed in a small case and powered by batteries.
- Ultrasonic cane. Let's write a program that will “beep” a buzzer at different frequencies, depending on the measured distance. For example, if the distance to an obstacle is more than three meters, the buzzer makes a sound once every half a second. At a distance of 1 meter - once every 100ms. Less than 10cm - beeps constantly.
Conclusion
The ultrasonic rangefinder is an easy-to-use, low-cost, and accurate sensor that has performed its function well on thousands of robots. As we learned in the lesson, the sensor has disadvantages that should be taken into account when building a robot. Good decision may become sharing ultrasonic rangefinder paired with a laser. In this case, they will level out each other’s shortcomings.Between objects. Ultrasonic rangefinders are a great help for professionals in this regard. These devices are capable of quickly measuring an area. Many models are equipped with a chip that allows you to store and process data. The devices differ from each other in measurement accuracy and functionality.
Ultrasonic rangefinder: instructions for use
To use the rangefinder, batteries are installed, and to start working, you must press the power button. Next, the user must select a function for the device. When measuring distances, you should pay attention to the units of measurement. In the model settings there is an option to save data. When calculating the area, it is worth indicating the values. To reset the data, you need to turn off the rangefinder.
When measuring the distance from the wall, it is necessary to install the device strictly perpendicular to the surface. When working with the device, you should pay attention to the permissible humidity and temperature parameters, otherwise the device may not work or show inaccurate data.
What is important when choosing
High precision and compactness are highly valued during repair work. The optimal measured distance is 20 meters. Batteries for the rangefinder are usually selected from the AAA series. Many devices have a minimum and maximum function. In this way, the obtained data can be quickly calculated.
The information on the screen should be clearly visible. It is worth paying attention to the operating conditions. Thus, a high-quality rangefinder can operate at a temperature of -10°C. The operating humidity of the equipment is approximately 55%.
Inexpensive rangefinders
There are many inexpensive rangefinders on the market that are manufactured with low power lasers. Their maximum range is 30 meters, and the accuracy of readings fluctuates around 94%. Many such devices are equipped with high-quality sensors. In addition, the models are able to operate in an economical mode. Batteries are usually installed with a small capacity. These devices differ in temperature conditions, and their operating humidity averages 55%.
The standard ultrasonic rangefinder HC SR04 is capable of storing about 20 values. The models also have a data calculation option. The batteries in rangefinders are AA series. It is also worth noting that in stores the user can find devices with a voice signal option. Judging by the reviews, such models are well suited for construction work.
Professional devices
Professional devices are distinguished by their long range. They are equipped with high-quality transmitters. At the same time, the chips are capable of storing more than 50 values. Some modifications also work at low temperatures. The accuracy of determining the values is about 98%. If we consider the Arduino (ultrasonic rangefinder), then its operating humidity is approximately 50%. Screens in devices are installed with high resolution and are equipped with backlighting.
You also need to remember that the models are able to quickly calculate the area. They have a small laser dot diameter. The devices are ideal for carrying out repair work on large construction sites. The maximum permissible temperature of professional rangefinders is about 55 degrees.
Devices for 15 meters
Devices with a range of 15 m, according to experts, are well suited for construction work in an apartment, but have some disadvantages. These modifications are usually equipped with small chips that can store no more than 20 values. In addition, these devices are poorly suited for indirect calculations. It is also worth noting that such models rarely have a minimum and maximum function. Screens are produced with low resolution. And many modifications only work at above-zero temperatures. Their housing is almost always protected from dust, but the models differ in the level of operating humidity.
20 meter models
20 meter rangefinders have recently become very popular and have good reviews. Many modifications are made with high-power lasers, but their dots differ in diameter. Modern devices (such as the Arduino ultrasonic rangefinder) are well suited for small construction sites.
These range meters differ in battery capacity. Some of them are equipped with a minimum and maximum function. These devices are rarely used for indirect calculations using the Pythagorean theorem. It is also worth noting that the chips in them are on average designed to store 30 values. The devices have different screens. And some modifications can boast high-quality backlights.
Reviews of the Bosch PLR 25 model
This ultrasonic rangefinder usually receives positive reviews. The modification has a lot of advantages, and among them is the presence of compact dimensions.
The housing of the device is protected from dust, and the laser is used in the second class. Some buyers praise the rangefinder for its high measurement accuracy. The chip in the device is capable of storing a lot of data. The connection of an ultrasonic rangefinder is also carried out quite quickly. Among the features, it is worth noting the presence of a minimum and maximum option. The device can be used at sub-zero temperatures. You can buy this device on the market for only 5,388 rubles.
Reviews of the Bosch PLR 15 model
This rangefinder is quite often used during repair work. The device has a well-protected case and can operate at high temperatures. At the same time, the rangemeter is not afraid of dust and dirt. It uses AAA batteries. It is also worth noting that the model is excellent for calculating data over long distances.
If we talk about the disadvantages, users note that the device takes a long time to turn on. It uses a weak battery, and the model is not able to remember much data. It is also worth noting that the rangefinder does not have a minimum and maximum option. The diameter of the laser dot is 5 mm. The devices can be used even at a temperature of 45 degrees. You can purchase it at a price starting from RUB 3,588.
Dexter Ultrasound Devices
This company mainly produces rangefinders for professional builders. Their range is approximately 45 m. Some modifications are made for indirect calculations using the Pythagorean theorem.
It is also worth noting that the devices are equipped with high-capacity AAA batteries. The case of most modifications is protected from moisture and dirt. On average, chips are designed to store more than 30 data. Devices have an option to calculate values. The device costs an average of 5 thousand rubles.
