Three liquid level transformers widely used in the

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Three liquid level transmitters widely used in the auto instrument inventory industry

liquid level transmitters are pressure transmitters for measuring liquid level, which are closely related to their measurement methods, installation methods and structures. Later, they are called liquid level transmitters. Liquid level transmitters are directly installed in pipelines or the existing difference between practice and theory Field transmitter on vessel. Since the isolation diaphragm is in direct contact with the liquid medium, it is not necessary to lead out the positive pressure side with a pressure pipe. Therefore, the liquid level, pressure and density of high temperature, high viscosity, easy crystallization, easy sedimentation and strong corrosion media can be measured, and then converted into 4 ~ signal output, which can also be classified as a liquid level gauge. Widely used liquid level transmitters include input liquid level transmitter, capacitive liquid level transmitter, single and double flange liquid level transmitter

I. input level transmitter

input level transmitter is based on the principle that the measured hydrostatic pressure is proportional to the height of the liquid, and uses the piezoresistive effect of diffused silicon or ceramic sensitive elements to convert the hydrostatic pressure into an electrical signal. It must also meet the requirements of accuracy indicators such as transverse vibration ratio, table acceleration uniformity and harmonic distortion specified in the verification regulation. After temperature compensation and linear correction, it must be converted into mADC standard current signal output

the input sensor can float on the surface of the measured liquid through its own structure, directly measure the liquid level height, and at the same time, convert the measured liquid related data into electrical signals through the silicon piezoresistive method and send them to the relevant collection equipment. The whole process is convenient and fast, and the use of the input sensor makes it unnecessary to manually measure the interior of the liquid under the same processing conditions, which greatly saves time, Increased efficiency

II. Capacitive liquid level transmitter

the core components adopt advanced RF capacitor circuit, which is converted into standard electrical signals (generally 4~20 MA) after accurate temperature compensation and linear correction by 16 bit single chip microcomputer. Hart, CANbus and 485 communication protocols can be selected for system configuration. The whole series of transmitters have self calibration function. Users can automatically calibrate the zero point and range through two buttons to meet the different requirements of various complex places

it is characterized by simple structure and no movable or elastic components, so it has high reliability and little maintenance. Generally, routine major, medium and small maintenance is not necessary; Multiple signal output, convenient for different system configuration; It is applicable to the liquid level measurement of high temperature and high pressure vessels, and the measured value is not affected by the temperature and specific gravity of the measured liquid and the shape and pressure of the vessel; It is especially suitable for the measurement of acid, alkali and other highly corrosive liquids; Perfect overcurrent, overvoltage and power polarity protection

III. flange current liquid level transmitter

flange liquid level transmitter can be divided into double flange and single flange. Single flange liquid level transmitter calculates the current liquid height through the change of liquid densitometer pressure according to the principle of pressure induction. Single flange liquid level transmitter can measure the accuracy of liquid level and density of various containers, including flat flange and plug-in flange. It is suitable for measuring high viscosity media or suspended liquids

as we mentioned above, liquid level transmitter is actually the application of pressure transmitter in liquid level measurement, so sometimes although the user actually measures the liquid level, it can also be called double flange differential pressure transmitter. Differential pressure transmitter is a transmitter that measures the pressure difference at both ends of the transmitter and outputs standard signals (such as 4~20ma, 1~5v). The difference between differential pressure transmitter and general pressure transmitter is that they have two pressure interfaces. Differential pressure transmitter is generally divided into positive pressure end and negative pressure end. Generally, the pressure of positive pressure end of differential pressure transmitter should be greater than the pressure of negative pressure section before measurement

among the above-mentioned liquid level transmitters, the liquid level transmitter based on the principle of pressure sensor is more widely used. There are crystalline liquid level transmitters that cannot use floating balls and pontoons, blue liquid level transmitters with viscosity, and single flange liquid level transmitters can be selected for open containers

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