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May 15, 2023
Infrared, ultrasonic, what are the differences between these two smart scale measurement methods?
Recently, Ms. Li's unit organized a physical examination, but in the first physical examination item - height test, Ms. Wang suffered a big "blow": Why is her height 1 centimeter shorter this year? 1 cm is not a small number in height! 159 cm and 160 cm sound like two grades! It is related to the image problem, Ms. Wang decided to think about it, what caused her height to "shrink". After asking the medical examiner, I found that there are various tools for measuring height, including infrared and ultrasonic... It sounds very high-end and foreign, but is it accurate? Ms. Lee is skeptical.
How to measure height with infrared and ultrasonic height measuring instrument?
In the past, when measuring height, a meter stick or a measuring tape could be stood against the wall to get a figure. It's different now, all kinds of high-tech means have come into play, infrared rays and ultrasonic waves have all been applied to the instruments for measuring height. So, what principle do these instruments use?
Most of the common infrared and ultrasonic height measuring instruments on the market use the principle of distance measurement. The operation is relatively simple and the measurement is fast.
According to the data, ultrasonic waves are sound waves with a frequency higher than 20,000 Hz. They have good directionality and strong penetrating ability. They are easy to obtain concentrated sound energy and have a long distance in water. Sterilization, etc. Ultrasonic ranging is mainly used in reversing radar, construction sites and some industrial sites, such as liquid level, well depth, pipeline length and other occasions.
The principle of using ultrasonic waves to measure distance is to continuously detect the echoes reflected by obstacles after ultrasonic waves are emitted, so as to measure the time difference between transmitting and receiving echoes, and then multiply the time difference by the wave speed to calculate the distance. It is this principle that is used to measure height. The difference is that when measuring height, the obstacle is the top of the person's head.
"The ultrasonic transmitter emits ultrasonic waves in one direction, and starts timing while transmitting. The ultrasonic waves propagate in the air, and return immediately when they encounter obstacles on the way. The ultrasonic receiver stops timing immediately after receiving the reflected waves. The propagation of ultrasonic waves in the air The speed is 340m/s, and according to the time recorded by the timer, the distance from the launch point to the obstacle can be calculated." An expert who designed an ultrasonic measuring instrument wrote in the paper.
The principle of infrared ranging is similar to that of ultrasonic ranging. Infrared is an electromagnetic wave with a wavelength from 760nm to 400μm in the spectrum, which is invisible light. Infrared rays have the function of non-diffusion. Using this principle, when infrared rays are emitted from the transmitter, they are reflected back and accepted when they encounter obstacles. The time difference in the middle is multiplied by the speed, and the distance can be measured, and then calculated. A person's height can be obtained.
So, is the height instrument based on the principle of distance measurement accurate?
For example, Ms. Li reported that her height has become shorter. On the Internet, some people reported that their height has become taller.
"I measured my height in the physical examination yesterday, and an interesting thing happened. My height was 1cm longer than the previous physical examination. I was wondering, maybe it's grown again. I said to myself, is this thing accurate?" On Weibo, a Netizens reported that their height has become taller. Many people also joined the discussion. Some people reported that they had done experiments repeatedly, using infrared height measuring equipment, and the final result: either taller or shorter. Why is this "high-end atmospheric and high-grade" instrument inaccurate?
"When using the infrared and ultrasonic height measuring instruments of the distance measurement method, sometimes the possibility of height error may indeed appear." Chen Yanru, a professor at the School of Electronic Engineering and Optoelectronics Technology of Nanjing University of Science and Technology, told reporters, "For example, some women's hairstyles are combed high, and their hair is also short. If it is very dense, the infrared rays will return when they encounter this 'obstacle'. If it is very sparse, it will not be able to achieve the effect of 'heightening'." In addition, if people wear large flowers or ornaments on their heads, they often It will also be mistaken for an obstacle, resulting in an increase in height.
In many cases, the inaccurate measurement may also be due to damage to the instrument components. "During production and operation, whether the components used are good or bad, and whether they are frequently calibrated and maintained may affect the accuracy." Chen Yanru suggested that if you are not sure about the accuracy of the measurement, you might as well ask the doctor to "calibrate" before measuring the height .
Experts said that, like the distance measurement method above, you can directly find a pole with a length of 1 meter, and then put a piece of white paper on it to simulate the appearance of a "person". Infrared or ultrasonic, when encountering an obstacle, it will naturally go back, and see if the measured data is 1 meter, and you will know whether the instrument is accurate. "Although the pole also expands with heat and contracts with cold, this is almost negligible, but it must be confirmed that the length of the pole is 1 meter. Of course, there are not many people who really go so seriously."
Ultrasonic height and weight measuring instrument is a popular measuring instrument at present and in the future. Because of its accurate measurement and high efficiency, it can measure 480 times per hour. It is very suitable for large-scale physical examinations, hospitals, shopping malls and other crowded places. High-tech ultrasonic measuring instrument, fully automatic measurement with voice broadcast, convenient and fast, if you are interested, please contact us.