Principle of Pressure Level Measurement
The static pressure level measurement method is based on the principle that the static pressure of the liquid column is proportional to the height of the liquid column, and the liquid level measurement is achieved by measuring the static pressure generated by the height of the liquid column. Differential pressure level meters are constructed using the principle that the static pressure generated by the liquid column also changes accordingly when the liquid level in the container changes. According to the principle of hydrostatics
<UNK> P = PB-PA = Ω gH
In the formula, PA is the static pressure(gas phase pressure)(Pa) of point A in a closed container; PB is a static pressure Pa at point B); H is the height of the liquid column(M); Hey is the liquid density(kg/m3).
The density of the medium to be measured is usually known. From the above formula, the pressure difference between points A and B is proportional to the height of the liquid level, so that the measurement of the liquid level H is converted to the problem of differential pressure measurement. Therefore, various pressure(differential pressure) measuring instruments can be used to measure the height of the liquid level.
A pressure meter used for liquid level measurement is an input liquid level meter, that is, a liquid level measuring instrument is put into the medium to be measured, with the change of liquid level, Pressure detection elements such as diffused silicon in the pressure transmitter convert static pressure to resistance signal for liquid level detection. Input-type liquid level meters can be directly put into the measured medium, using a solid state structure, unmovable components, high reliability, long service life, and very convenient for installation and use, and can measure paste from water, oil to viscosity. It is not affected by the bubble, deposition, and electrical characteristics of the measured medium, has no material fatigue and wear, and is not sensitive to vibration and impact. It is widely used in urban water supply, drainage, reservoirs, and open containers.
For the liquid level in open or closed containers, it can be determined by detecting the pressure difference between the measured liquid surface and the low Zui liquid level(reference liquid level). The liquid level of the open vessel is measured, the liquid level change range of the open vessel is H, and the positive Chamber of the differential pressure transmitter is in the same plane as the low Zui liquid position; Because the gas phase pressure is atmospheric pressure, the negative pressure Chamber of the differential pressure transmitter can pass through the atmosphere. At this time, the pressure acting on the positive pressure chamber is the static pressure generated by the liquid level height, IE
PA = 0
<UNK> P = PB = Ω gH
The measured liquid level is positively proportional to the differential pressure. From the differential pressure indicator of the differential pressure transmitter, the value of the measured liquid level can be known.