超声波液位计，物位的定义：“物位”一词统指各种设备和敞开或密闭的容器中液体或固体物料的表面位置。对应不同性质的物料又有以下的定义：

　　1、液位指设备和容器中液体介质表面的高低.

　　2、料位指设备和容器中所储存的块状,颗粒或粉末状固体物料的堆积高度.

　　3、界位指相界面位置：容器中两种互不相溶的液体,因其重度不同而形成分界面,为液-液相界面;容器中互不相溶的液体和固体之间的分界面,为液-固相界面.液-液,液-固相界面的位置简称界位。

　物位是液位,料位,界位的总称.对物位进行测量,指示和控制的仪表,称物位检测仪表。物位检测仪表的分类：由于被测对象种类繁多,检测的条件和环境也有很大差别,所以物位检测的方法有多种多样,以满足不同生产过程的测量要求.物位检测仪表按测量方式可分为连续测量和定点测量两大类.连续测量方式能持续测量物位的变化(连续量，输出标准连续量信号)定点测量方式则只检测物位是否达到上限,下限或某个特定位置,定点测量仪表一般称为物位开关(点位，输出开关量信号)按工作原理分类,物位检测仪表有直读式,静压式,浮力式,机械式,电气式等。

Ultrasonic level gauge, definition of material level: the term "material level" refers to the surface position of liquid or solid materials in various equipment and open or closed containers. There are the following definitions for materials of different properties:

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

2. Material level refers to the stacking height of block, particle or powder solid materials stored in equipment and containers

3. Boundary position refers to the position of the phase interface: two kinds of mutually insoluble liquids in the container form the composition interface due to their different gravity, which is the liquid-liquid interface; the interface between mutually insoluble liquids and solids in the container is the liquid-solid interface. The position of the liquid-liquid and liquid-solid interface is abbreviated as the boundary position.

Material level is the general term of liquid level, material level and boundary level. It is the instrument for measuring, indicating and controlling the material level, which is called material level detection instrument. Classification of level measuring instruments: due to the wide variety of objects to be measured and the different testing conditions and environments, there are various methods of level detection to meet the measurement requirements of different production processes. Level measuring instruments can be divided into two categories: continuous measurement and fixed-point measurement. Continuous measurement can continuously measure the change of level (continuous quantity, continuous output standard The fixed-point measuring method only detects whether the material level reaches the upper limit, lower limit or a specific position. The fixed-point measuring instrument is generally called the material level switch (point position, output switch signal) according to the working principle. The material level measuring instrument has direct reading type, static pressure type, buoyancy type, mechanical type, electrical type, etc