Ultrasonic level sensor and input level sensor which is more accurate

- Jun 12, 2019-

 

Today, science and technology have invented countless kinds of liquid level measurement methods, from ancient scales to modern photoelectric, ultrasonic, and radar measuring instruments. The liquid level sensor and liquid level switch have become "a good hand" in the fields of petrochemical, metallurgy, electric power, pharmaceutical, water supply and drainage, environmental protection, etc., and play an important role in the industrial field. OSENON engineers introduce you to the ultrasonic level sensor and the input level transmitter which is more accurate?


Ultrasonic liquid level sensor working principle


Ultrasonic liquid level sensor


Ultrasonic wave is a kind of mechanical wave whose vibration frequency is higher than sound wave. It is generated by the vibration of the transducer wafer under the excitation of voltage. It has high frequency, short wavelength, small diffraction phenomenon, especially good directionality, and can be oriented as a ray. Characteristics such as communication. Ultrasonic penetration of liquids and solids is very large, especially in sunlight opaque solids, which can penetrate depths of several tens of meters. When an ultrasonic wave hits an impurity or an interface, it will produce a significant reflection to form a reflection into an echo, which can produce a Doppler effect when it hits a moving object. Therefore, ultrasonic testing is widely used in industrial, national defense, biomedical and other fields. Ultrasound is used as a detection means, and ultrasonic waves and ultrasonic waves must be generated. The device that performs this function is an ultrasonic sensor, which is customarily called an ultrasonic transducer, or an ultrasonic probe.


However, the ultrasonic liquid level sensor has a certain dead zone. It is well known that the so-called blind zone is caused by the physical characteristics of the ultrasonic wave. Because the ultrasonic probe has a small distance from the outermost surface, the reflected echo cannot be detected normally. This small distance is called ultrasonic wave. The dead zone of the level sensor.


The reflected wave cannot be detected normally within this small distance. This is because the ultrasonic level sensor cannot detect the reflected echo at the same time when transmitting the ultrasonic pulse. Moreover, since the transmitted ultrasonic pulse has a certain time width, and the sensor has residual vibration after the ultrasonic wave is emitted, the ultrasonic liquid level sensor cannot detect the reflected echo. Therefore, the blind spot of the ultrasonic liquid level sensor is different according to the range, and the blind zone is different. If the range is small, the blind zone is small and the range is large, and the blind zone is large. But usually it is between 30cm-50cm. Therefore, it is usually necessary to think about entering the time zone of the ultrasonic level sensor of the device. In special occasions, the blind spot is required to be small. This time can be considered as a small blind spot ultrasonic level sensor, and the dead zone is usually only 4-6cm. However, its range is small, as long as 0.6m.


In the category of many liquid level measurement, because of the space constraints, the constraints of the device conditions, the ultrasonic level sensor with a small blind spot is required. Therefore, when the highest level to be measured enters the blind spot, the appearance will not be detected correctly and an error will occur. If necessary, the level gauge can be raised. In addition, for the application of the liquid level, the requirements for the blind zone are generally not high in the field of detecting the water level, but the requirements for the range are relatively high, and vice versa for the application of some water tanks.


Working principle of input level sensor


Working principle of input level sensor


The input type liquid level sensor is one of many classifications of liquid level sensors, and is mainly used for measurement of hydraulic pressure, liquid level, etc., and is widely used in various fields. The input type liquid level sensor generally uses the piezoresistive effect of diffused silicon or ceramic sensitive components to convert the static pressure into an electrical signal, which is temperature compensated and linearly corrected. Converted to 4-20mADC standard current signal output. The input type liquid level sensor is a static pressure level measurement. In a liquid medium, the pressure generated at a certain depth is generated by the weight of the medium itself above the measurement point. It is proportional to the density of the medium and the local gravitational acceleration. Therefore, the physical quantity measured by the input level sensor is actually the pressure, which can also be known by the calibration unit of the sensor. The actual liquid level must be obtained by conversion after knowing the two parameters of density and gravity acceleration. Such conversion is usually carried out in the industrial field by means of secondary instruments or plc. Generally applicable to liquid level measurement of various media in petrochemical, metallurgy, electric power, pharmaceutical, water supply and drainage, environmental protection and other systems and industries.


Input type liquid level: input liquid bottom, contact type measurement, poor precision, large relationship between measured value and density, need atmospheric compensation, cable suspension installation should be fixed, and moisture is easy to condense. The disadvantage of the input type liquid level sensor is that the measurement signal needs to be converted; the high temperature medium temperature exceeding 125 °C cannot be measured; the density of the measurement medium must be uniform.


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