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technical article
Definition of level and classification of level detection instruments
2011-3-9 9:57:39

Definition of level

The term "level" refers collectively to the surface location of liquid or solid materials in equipment and containers. Corresponding materials with different properties have the following definitions.

1. Liquid level refers to the level of the surface of the liquid medium in the equipment and container.

2. Material level refers to the stacking height of solid, granular or powdery solid materials stored in equipment and containers.

3. Boundary refers to the position of the phase interface. The two immiscible liquids in the container form a liquid-liquid phase interface because of their different gravity; the liquid-solid interface is the liquid-solid phase interface between the liquids and solids that are incompatible in the container. The position of the liquid-liquid, liquid-solid phase interface is referred to as the boundary level.

Level is the general term for liquid level, material level and boundary level. Instrument for measuring, indicating and controlling the material level.

Classification of level measuring instruments

Because there are many kinds of objects to be measured, the measurement conditions and environment are also very different, so there are various methods for level measurement to meet the measurement requirements of different production processes. Level measuring instruments are divided into two categories: continuous measurement and fixed-point measurement. The continuous measurement method can continuously measure the level change. The fixed-point measurement method only detects whether the material level reaches the upper limit, the lower limit, or a specific position. The fixed-point measurement instrument is generally called a material level switch. Classified according to the working principle, level measurement instruments are direct reading, static pressure, buoyancy, mechanical, electrical and so on.

1. Direct-reading level detection instrument, adopts side wall window or bypass pipe to directly display the height of the level in the container. The method is reliable and accurate, but it can only be indicated locally. Mainly used for liquid level detection and low pressure occasions.

2. Hydrostatic level detection instrument, based on hydrostatic principle, suitable for liquid level measurement. The height of the liquid surface in the container is proportional to the static pressure formed by the liquid column weight t. When the density of the measured medium is constant, the liquid level can be measured by measuring the pressure at the reference point. This type of instrument has pressure, blow and differential pressure.

3. Buoyancy type level measuring instrument, its working principle is based on Archimedes's law, suitable for liquid level measurement. Floats floating on the liquid surface or buoys immersed in liquid will have corresponding changes in the buoyancy when the liquid surface changes, so that the liquid level can be detected. Such instruments include various float-type level gauges, float-type level gauges, and the like.

4.Mechanical contact level measurement instrument to achieve level measurement by mechanical force when the position level probe is in contact with the material surface. These instruments are heavy hammer type, rotor type and tuning fork type.

5. Electrical level measuring instrument, which places the electrical level sensitive element in the measured medium. When the level changes, its electrical parameters such as resistance and capacitance will also change. The level can be known by detecting these changes in electricity.