The Difference between Radar Level Measurement and Ultrasonic Level Measurement
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The Difference between Radar Level Measurement and Ultrasonic Level Measurement What’s the difference between radar level measurement and ultrasonic level measurement? What’s the principle of both? What kind of conditions are they used in? What’s the measurement accuracy of these two? Here we explain these issues and talk about both gauges. Radar level gauge using emission - reflection - reception mode. Radar level gauge antenna emits electromagnetic waves, the waves reflected by the surface of the measured object, and then received by the antenna; the electromagnetic wave from the transmitter to the receiver time and proportional to the distance to the surface, the relationship is as follows: D=CT/2 D: distance from radar level gauge to level C: Speed of light T: Running time of electromagnetic wave In practice, radar level gauge has two ways which is frequency modulated continuous wave and pulsed wave type. Using frequency modulated continuous wave, power consumption, need adopt the four-wire, and the electronic circuitry is complex. The use of radar pulse wave, low power consumption, can wire the 24VDC power supply, easy to implement intrinsically safe, high accuracy, applies more broadly. Ultrasonic using sound waves, and radar using electromagnetic wave, this is the greatest difference. And ultrasonic waves penetrating power and directivity are stronger than electromagnetic wave, and this is why the ultrasonic probe is more popular today. The distinction of main applications: 1. An ultrasonic precision less than radar. 2. Radar relatively higher price. 3. Radar should consider the dielectric constant. 4. Ultrasonic can not be applied to vacuum, the condition which vapor content is too high or there is a bubble level and other working conditions. 5. Radar measurement range is much larger than the ultrasound. 6. Radar has flared, rod, cable type, the relative ultrasound can be applied to more complex conditions. We generally exceeding 20 kHz sound frequency sound waves called ultrasound, ultrasound is a mechanical wave, which is characterized by high frequency, wave length, the phenomenon of diffraction is small, and additionally it has good direction, can be directed rays spread. Ultrasound has small attenuation in liquid and solid, thus penetrating ability is strong, especially in light opaque solid, ultrasonic can penetrate tens of meters, it will reflect if encounter impurities or interface, ultrasonic level measurement is use this feature. In the ultrasonic testing technique, regardless of the kind of ultrasound equipment, must be converted electrical energy to the ultrasonic transmitter, and then receive back into an electric signal, to accomplish this function, this device is called an ultrasonic transducer, also known as probes. Place the probe in the liquid under test above, downward firing ultrasonic waves through the air medium, is reflected back across the water surface, and is received by the transducer and converted to electrical signals, electronic detection section detects this signal after it becomes empty signal for display and output. Transmitted by the ultrasonic principle known in the medium, if the medium pressure, temperature, density, humidity and other conditions are fixed, then the ultrasonic propagation velocity in the medium is a constant. Therefore, when measuring the time from ultrasound reflecting to receive, then can be converted through the ultrasound distance, i.e. the level of the data obtained. Ultrasound has blind spots, the installation must be calculated and set aside the sensor mounting position and the distance between the measuring liquid. |
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