Direct Error Compensation Precision Ultrasonic Distance Meter

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Ultrasonic distance meter uses the propagation speed of sound to calculate the distance of the measured object. As a modern measurement tool, it has been widely used. However, the measurement accuracy of ultrasonic rangefinders has inherent limitations. Most ultrasonic rangefinders use air as the transmission medium to transmit sound waves. Due to changes in ambient temperature, the accuracy of ultrasonic rangefinders is directly affected by changes in ambient temperature. Most existing ultrasonic distance meters use temperature sensors to compensate for errors caused by temperature changes. Since the temperature sensor is packaged in the ultrasonic sensor, it is not only far away from the object being measured, but also cannot directly measure the temperature of the transmission medium. Its measurement It is only the temperature of the environment of the ultrasonic sensor, or the temperature of the sound wave transmission medium is calculated through the distribution theory of the temperature field. This indirect temperature error compensation method cannot fully meet the needs of measurement accuracy.

Direct error compensation precision ultrasonic distance meter, including piezoelectric ceramic transducer, pulse generator, benchmark, signal receiving amplifier, inverter, digital-to-analog conversion, microprocessor, communication interface and display system, etc. The key point is that the sound wave transmitting end of the ultrasonic rangefinder is connected to a benchmark of fixed length. The benchmark is located at the geometric axis of the emission wave cone. The other end of the benchmark has a circular or regular polygonal reflection facet perpendicular to the emission wave. , the area of this plane is 3 to 8 times the cross section of the benchmark, and the axis of the benchmark passes through the geometric center of the reflective facet to reflect sound waves. This rangefinder has the advantages of high measurement accuracy, reliable performance, simple structure, and can work in harsh environments. It is suitable for measuring various targets.

Currently, the existing ultrasonic range finders on the market have the above-mentioned shortcomings that the measurement accuracy cannot be guaranteed when measuring the distance of the measured target. We provide an ultrasonic range finder that adopts direct error compensation and has high measurement accuracy. .

A direct error compensation precision ultrasonic distance meter, which includes a piezoelectric ceramic transducer, a pulse signal generator, a benchmark, a signal receiving amplifier, an inverter, a digital-to-analog conversion, a microprocessor, a communication interface and a display system. The key point is that the sound wave transmitting end of the ultrasonic rangefinder is connected to a benchmark rod, and its position is at the geometric axis of the transmitting wave cone. The length of the benchmark rod is determined according to actual needs. The material of the benchmark rod is a metal or non-metallic material with a small thermal expansion coefficient. . The other end of the benchmark has a small plane perpendicular to the emitted wave. The shape is a circle or a regular polygon. The area of the plane is 3 to 8 times the cross section of the benchmark. The axis of the benchmark passes through the geometric center of the reflection facet for reflection. sound waves. During measurement, based on the error compensation coefficient obtained from the actual length of the benchmark and the length of the benchmark measured by the ultrasonic sensor, the distance to the measured target can be obtained after the microprocessor performs calculations.

The error compensation benchmark is adopted. The error compensation coefficient generated during the measurement eliminates the measurement errors caused by the temperature changes of the sound wave transmission medium and other environmental factors. Therefore, it has high measurement accuracy, reliable performance, and can be used in harsh environments. It has the advantages of working in a special environment, its structure is simple, it is easy to use, and it has a wide range of applications.

Description of the drawings

Figure 1 is a schematic structural diagram of the utility model.

                                                                          Figure 1 

Figure 2 is a working principle diagram of the present utility model.

                                                                                                                     Figure 2

Specific implementation mode, the structure of this rangefinder is shown in Figure 1, a direct error compensation precision ultrasonic rangefinder, which mainly includes a piezoelectric ceramic transducer, a pulse signal generator, a benchmark, a signal receiving amplifier, an inverter processors, digital-to-analog conversion, microprocessors, communication interfaces and display systems. The communication interface is located on the end cover (1) of one end of the housing (3), the liquid crystal display (2) is located on the outer surface of the housing (3), and the communication interface and the display screen (2) communicate with the microprocessor through a communication cable. The piezoelectric ceramic transducer, pulse signal generator, signal receiving amplifier, inverter, digital-to-analog conversion and microprocessor are installed in the inner cavity of the housing. The key point is that the benchmark (4) is connected to the inner wall of the shell through a fixed frame in the shell, and is located on the end face of the transducer, at the geometric axis of the emitting wave cone. The benchmark (4) is made of a material with a low thermal expansion coefficient. , its length can be determined according to actual needs. The other end of the pole has a reflective facet (5) perpendicular to the emitted wave. The area of this plane is generally 3 to 8 times the cross section of the benchmark.

Here's how it works:

The pulse signal generator inside the ultrasonic rangefinder generates a pulse signal of a certain frequency, which excites the transducer to generate pulse ultrasonic waves. The transducer will receive two reflected ultrasonic waves, one is the sound wave reflected by the benchmark facet (5), The other is the sound waves reflected by the target object, which are converted into electrical signals and sent to the signal amplifier. After amplification, they are sent to the microprocessor through the inverter for digital signal processing. Through preliminary calculations, the benchmark for the initial measurement of the ultrasonic rangefinder is calculated. The length L (the distance from the transducer end face to the reflective facet of the benchmark) and the target distance Lc (the distance from the transducer end face to the target end face), since the actual length Lo of the benchmark is known, a direct error compensation coefficient can be obtained α=Lo/L, the error compensation coefficient α is used to eliminate the influence of temperature changes of the air medium and the surrounding environment on the target distance measurement accuracy. After considering the error compensation,

Finally, the actual measured distance L1=αLo of the measured target object is calculated.

In order to further improve the measurement accuracy of the sensor, the distance to the same point can be measured multiple times, and the average measurement value is used to obtain the final measurement distance D:

D=(di)-dmax-dmin]/(n-2)

Zdi - the sum of n measurements

dmax - maximum value among n measurements

dmin - minimum value among n measurements

n - the number of measurements at the same point, it is recommended that n=10 or so

All calculations are processed through the built-in software of the ultrasonic distance meter, and the measured data are automatically processed and displayed on the LCD display or transmitted to other controllers.

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