[knowledge] how does the pressure transmitter measure the liquid level?

The application of pressure transmitter when it works, it must contact with the measured medium directly It often operates in high temperature, low temperature, corrosion, vibration, impact and other environments Whether it can operate normally and reliably in the project site depends not only on the product quality, but also on the optimized engineering design, reasonable model configuration and correct field maintenance Pressure transmitter products are widely used in iron and steel, chemical industry, papermaking, sewage treatment, tap water, heat, power, food, non-ferrous and other industries In addition to measuring pressure, pressure transmitter can also be derived from many uses, such as using differential pressure transmitter to measure flow, using the gravity of liquid to measure liquid level Working principle of hydrostatic level transmitter working principle of hydrostatic level transmitter is: the static pressure of a point in the liquid is directly proportional to the distance from the point to the liquid level, that is, P = ρ GH Among them: p-pressure of measured point, ρ - density of medium, G-acceleration of gravity, h-height from measured point to liquid level For the determined measured medium ρ, G is a constant, so the change of the position from the measured point to the liquid level is only related to the measured P pressure When measuring the liquid level in an open container, a pressure transmitter is required When measuring the liquid level of the closed pressure vessel, two pressure transmitters or one differential pressure transmitter can be considered, i.e one for the lower limit and one for the upper limit Their output signals can be subtracted to measure the liquid level At this time, the differential pressure transmitter is generally selected It can also be used to measure the density of the medium when the liquid level and pressure in the container are constant Liquid level measurement of open container liquid level measurement of open storage tank means that the tank is open to the atmosphere, and any change of atmospheric pressure will affect the process fluid pressure in the tank In this kind of liquid level measurement application, atmospheric pressure can be measured at the low pressure side of the transmitter, thus eliminating the influence of atmospheric pressure on the liquid level of the storage tank The high pressure side of the transmitter is connected to the tank so that the actual level in the tank can be measured Liquid level measurement of closed containers for closed containers, due to the internal isolation from the atmosphere, when the process fluid fills or empties the tank, the pressure in the tank may change from positive pressure to vacuum This change in tank pressure will directly affect the measured level unless compensated for This can be done by connecting the low side pipe of the differential pressure transmitter to the top of the water tank Therefore, when measuring the liquid level of closed tank, differential pressure transmitter must be used In chemical production, the medium of flange type differential pressure transmitter often encounters problems such as impurities, crystalline particles or agglomeration, which is easy to block the connecting pipeline At this time, flange type differential pressure transmitter is needed The closed system composed of capsule, capillary and measuring chamber is filled with silicone oil, which is used as pressure medium to prevent the measured medium from entering into capillary and transmitter, so as to avoid blocking Flange type differential pressure transmitter is divided into single flange type and double flange type according to its structure Only one flange is needed to connect the pipeline between the vessel and the transmitter, which is called a single flange differential pressure transmitter For the closed vessel with the upper end isolated from the atmosphere, because the upper space and the atmospheric pressure are mostly different, two flanges must be used to guide the liquid and gas pressure to the differential pressure transmitter, which is a double flange differential pressure transmitter Our products are widely used in power, chemical, metallurgy, coal, water engineering, petroleum, medical, food and other industries