从酿造到聚合的工业和化学过程取决于准确量的气体或液体的递送。可以根据质量或每单位时间的质量或数量来衡量交货率，并且在它们之间进行选择是基于应用程序的。在许多情况下，体积流量测量足够，尤其是在已知和稳定的压力和温度的情况下。但是，由于质量流量测量直接表明存在的分子量，因此它具有免疫密度变化的优势。
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大多数工程师都习惯了测量体积流量的众多方法。通常，质量流量测量鲜为人知和理解。这篇欧米茄工程文章解释了如何直接测量质量流量（例如通过热量损失）和间接测量（通过压降来推断），并突出显示某些商业上可用的适用特征质量流量计s.
质量表类型和操作原则
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铜箱
这mostly extensively used types of meters are differential pressure, thermal mass and Coriolis.
差分流量计
诸如磁盘等磁盘的障碍物被放置在层流的区域内，并在两侧测量流体压力。在上游侧的压力将更高，读数的差异相对于两个读数点，粘度，体积流量和管道直径之间的距离，如Poiseuille方程式所示。然后对压力和温度进行校正，以产生标准化的质量流量。
热质量流量计
这se are available in two designs: inserted probe and heated sample tube. Both derive mass from the specific heat capacity of the fluid (thus negating density variations) hence it is essential to know this property. Thermal mass flow meters are suitable for low gas flow rates.
In a heated sample tube mass flow meter, all or some of the flow passes through a high precision tube. Heat is applied to the tube and the variation in temperature measured. The difference in temperature between the two points specifies how much energy the fluid has absorbed, which relies on the mass moving through the tube.
插入的探针质量流量计使用相同的原理，但有两个RTD探针位于流中。上游传感器测量流体温度，而第二个传感器加热到温度的温度大于第一传感器的温度。热量以与质量流速相等的速率从第二传感器转移到流体。
科里奥利质量流量计
Coriolis质量流量计通过惯性测量质量。密集的气体或液体流过由小执行器振动的管。这种加速度在与质量成比例的管子上产生可测量的扭曲力。指定质量流量，而无需任何流动的流体知识。更精致的科里奥利仪使用双弯曲管来降低压降和更高的灵敏度。
Factors Influencing Accuracy
这accuracy of the differential pressure mass flow meter is affected by three factors. First, the measurement is inferred from pressure and temperature, so thus error in these reflects in the final result. Second, there are expectations about the viscosity and the degree to which laminar flow is attained (turbulence affects flow via the obstruction and produces misleading pressure measurements). Third, and perhaps the most significant, refers to the fact that the orifice may wear, becoming bigger over time and thus reducing the pressure drop. Based on the fluid passing through, there is also a risk of partial blockage.
When using thermal mass flow meters it is essential to consider the possible influence of:
- 温度检测器上的水分凝结：饱和气体可能会产生水分，从而导致读数不良，最终导致腐蚀。
- 颗粒物积累：如果传感器上残留物的积累阻碍热传递，也可能发生低读数。
- Error in specific heat capacity assumption: Stemming from inconsistencies or variation in gas composition.
Additionally, thermal mass flow meters require time to reach a steady-state operating temperature. As soon as the device is powered-up, readings should not be taken.
科里奥利的质量流量计虽然被认为是最准确的，但容易受到液体气泡引起的错误。这些允许在管中“飞溅”，产生噪声并改变管振动所需的能量。巨大的空腔不足地增加了管振动所需的能量，从而导致完全故障。另外，将流体分离为液体和气体会产生对管振动的阻尼作用。
Applications for Mass Flow Meters
差异质量流量计（s）在任何可以安全地假设流体具有可靠的粘度，最好的地方，而温度不变的地方。气体的可压缩性会导致问题，但是液体分配和处理应用通常效果很好。必须为通过仪表的压力下降而允许。当仪表打开后必须立即进行读数时，它们很有用。
这rmal mass flow meters work with both gases and liquids. They are used extensively in:
- Chemical processing
- 过滤和泄漏检测
- Nuclear power facility air monitoring
- 半导体工艺气体测量
热质量流量计的其他常见应用包括实验室分析，例如气相色谱。
Coriolis mass flow meters, as the most accurate, and also the most expensive, technique, are the predominant type of meter employed in scientific applications where they measure both corrosive and clean liquids and gases. They are also found in:
- Chemical processing
- Petroleum and oil
- 废水处理
- Pulp and paper processing
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纸浆和纸质加工
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Petroleum and Oil
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废水处理
具有直接管设计的仪表更毫不费力地清洁，因此首选用于饮料和食品应用以及药品。他们还处理采矿作业中通常发现的浆液。
这最新的in Mass and Volumetric Flow Meter Technology
这OMEGA®FMA6600/6700系列仪表are multiparameter mass flow devices that have the potential to provide pressure, flow and temperature measurements. Intended for use with gases, mass flow is measured with the help of the heated sample tube principle. These meters handle gas flows from 0.15 to 100 LPM and are accurate to ±1% and accuracy ±11/2全尺度。
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不锈钢FMA3100/3300st thermal质量流量计系列还设计用于干净的气体。使用加热的样品管原理，这些能力能够将流速从0.4到20 SCCM到10至500 lpm，温度灵敏度为±0.15％，重复性±0.25％，全尺度。
对于最合适的差压力质量流量计的情况，FMA-1600A的范围为0至0.5 SCCM，最高为0至3,000 SLM。它包括30多个气体校准，并以同时方式显示压力，温度，体积和质量流量。FMA-1600A系列的典型准确性为±（读取 + 0.2％全尺度的0.8％）。
要点
可以通过差异压或直接使用Coriolis效应或特定的热容量来间接测量质量流速。
Coriolis mass flow meters generate the most accurate for most liquids but are expensive. They have the benefit of not requiring any knowledge about the fluid being carried.
热质量流量计是一种不太准确但仍直接测量的方法。他们确实需要了解液体的特定热容量。
差异质量流量计生成通过Poiseuille方程得出的间接测量，该方程必须改变流体压力和温度。当流体不可压缩时，这很好。
此信息已从Omega Engineering Ltd提供的材料中采购，审查和改编。欧洲杯足球竞彩
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