Working principle of double-flange level transmitter

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Before understanding the working principle of double-flange level transmitters, let’s first learn what a level transmitter is, what a double-flange level transmitter is, how to distinguish between single-flange and double-flange level transmitters, and the working principle of level transmitters. I. Overview of Level Transmitters Level transmitters operate on the principle that the static pressure of a liquid is proportional to its height; they utilize the piezoresistive effect of diffused silicon or ceramic sensing elements to convert this static pressure into electrical signals. After temperature compensation and linear correction, it is converted into a standard 4-20 mA DC current signal for output. The sensor part of this product can be directly immersed in liquid, while the transmitter part can be fixed using flanges or brackets, making it extremely convenient to install and use. II. Overview of Double-Flange Level Transmitters A double-flange level transmitter, also known as a double-flange gauge, is based on a single-flange differential pressure transmitter; an additional flange is added, resulting in two flanges – one designated as H “high-pressure side or positive pressure side” and the other as L “low-pressure side or negative pressure side”. There is also a certain length of stainless steel capillary tube between the transmitter and the two flanges. Using a capillary flange transmitter for measurement is equivalent to extending the diaphragm in the transmitter’s sensing element to the opening of the device, which effectively eliminates the impact of viscous, corrosive, or media with severe phase changes on the measurement. III. Differentiation between single-flange and double-flange level transmitters 1. A single-flange design means that the positive pressure side of the transmitter features a flange structure that is directly connected to the interface with the medium being measured, while the negative pressure side uses a pressure lead to connect the measuring medium to the transmitter’s chamber. 2. Double flange refers to a transmitter in which both the positive and negative pressure sides have a flange structure, allowing it to be connected directly to the containers or pipes that need to be measured. The advantages are easy installation, convenient calibration, and no need for range transfer. IV. Working Principle of Level Transmitters Level transmitters are simple and reliable instruments for measuring the liquid level in tanks. They utilize the principle of P=ρgh to measure pressure differences, thereby determining the liquid level; the height of the liquid level is directly proportional to the pressure difference detected by the level transmitter. The process connection for level transmitters typically uses diaphragm flanges, with silicone oil filled inside the diaphragm to serve as the medium for transmitting pressure. Liquid tanks are generally divided into open-top tanks and pressurized tanks. In open-top tanks, the upper part is in contact with the atmosphere; a level transmitter used to measure the liquid level in such tanks only needs to be connected to the process flange on the high-pressure side, while the low-pressure side remains in communication with the atmosphere. Pressure vessels, on the other hand, require diaphragm flange connections on both the high-pressure and low-pressure sides of the level transmitter in order to measure the pressure difference between these two sides. V. Working Principle of Double-Flange Level Transmitters A double-flange level transmitter is a pressure sensor component used to prevent the medium in the pipeline from entering the transmitter directly; it is connected to the transmitter through a capillary tube filled with fluid. It is used to measure the level, flow rate, and pressure of liquids, gases, or vapors, and then converts these values into a 4–20mA DC signal for output. 1. Principle of differential pressure level gauge: it utilizes the principle of pressure difference resulting from differences in liquid level. Differential pressure level gauges are divided into two types: one is the single-flange level gauge, used for measuring levels in open containers, and the other is the double-flange type, used for measuring levels in closed containers. 2. A capacitor is formed by each of the measuring diaphragm and the electrodes on the insulating sheets on both sides. When the pressures on both sides are not equal, it causes the measuring diaphragm to move. This circuit detects the digital signal superimposed on the 4-20mA signal and transmits the required information through the loop. Its displacement is proportional to the pressure difference; therefore, the capacitances on both sides are not equal. Through oscillation and demodulation processes, this is converted into a signal that is proportional to the pressure. 3. When measuring media that are corrosive or contain crystalline particles, as well as those with high viscosity or prone to solidification, in order to avoid corrosion or blockage of the pressure transfer lines, a flanged differential pressure transmitter can be used: the flange of this transmitter can be directly connected to the flange on the container. The sensing element, namely the metal diaphragm box, is connected to the transmitter’s measurement chamber through capillaries. A silicone oil fills the closed system formed by the diaphragm box, capillaries, and measurement chamber, serving as a pressure transfer medium and helping to isolate the transmitter from the medium being measured. 4. The double-flange level transmitter is rather special; it consists of two pressure-sensitive diaphragms, positive and negative, each of which is connected to the positive and negative chambers of the gauge through a sealed capillary tube filled with silicone oil. After installation, the flange connecting the negative pressure pipe rises, and the silicone oil inside exerts pressure on the negative pressure chamber. Jiangsu Huike Automation Instrument Co., Ltd. offers you professional advice on product selection as well as reliable products. If you have any questions, feel free to call us; we will assign professional technicians to assist you.