GB/T 38617-2020Industrial-process measurement and control instruments terminology - Level measuring instruments terminology (English PDF)

2.1 General terms

2.1.1 Level

The interface position of two different phase media or immiscible liquid media.

Note. It is usually expressed by the vertical distance between the interface and the reference surface.For applications where there is an angle of repose, the interface between the measured point and the reference surface is also used.

To express the vertical distance between them. Levels in industrial processes include. liquid level (gas-liquid interface position), material level (gas-solid interface position), liquid-liquid interface, liquid-solid interface. The above definition also applies to a vacuum environment where there is no gas phase.

2.1.2 Level [measurement] instrument

Device for measuring, displaying, alarming and controlling the material level.

Note. Including level gauge and level switch.

2.1.3 Level meter (gauge)

Level measuring instrument for continuous measurement of level.

Note. Including the level gauge to measure the liquid level and the level gauge to measure the solid material.

2.1.4 Level switch

Level measuring instrument for fixed point (limit) type measurement of level.

Note. Including the level switch to measure the liquid level and the level switch to measure the solid level. The digital signals include SPST, SPDT, DPDT, 0/1, 8/16mA,

Namur>=2.6mA/<=0.6mA, DCPNP, DCNPN, frequency signal (high frequency/low frequency), solid state relay status output, etc.

2.1.5 Level Transmitter

It measures the continuous level signal and converts the level signal into a recognizable standard analog or communication signal output instrument.

Note. Including liquid level transmitter for measuring liquid level, level transmitter for measuring solid material level. Common standard analog output signals are current output type and voltage output type. The communication methods between the instrument and the external system usually include HART, Modbus, Profibus, and FoundationBus.

2.1.6 Surface roughness

The roughness of the surface of solid materials such as lumps, particles and powder.

Note. The average diameter of particles is usually used to characterize.

2.1.7 Angle of repose

The slope formed by the natural accumulation of solid materials.