The primary factors affecting the accuracy of the flow appearance, excluding the flow appearance of the principle and structure of the cause itself, the external factors affecting the accuracy of the primary attributed to the following two aspects.

(1) the physical properties of the fluid

In the experiment commonly used medium for water, air and oil. And in the field use will be faced with tens of thousands of various fluids, their physical properties (such as density, viscosity, electrical conductors, thermal conductivity, speed of sound, composition ......) are different from the commonly used in the experiment in the medium, will affect the flow of the appearance of the accuracy of the flow to a greater or lesser extent. However, the physical properties of these fluids can be found through a number of engineering manuals, and to give a correction to mitigate its impact. This is also an important element of the flow appearance of intelligence.

(2) Fluid properties

In the field through the flow of appearance of the fluid may not be as clean as the fluid used in the laboratory, they may have sediment, corrosive. After using a period of time, but also in the pipe edge inspection parts on the occurrence of scale, wear and corrosion. Deposits on the pipe wall will change the wall thickness and roughness of the pipe. For the standard orifice plate will change the semi-finish value, constituting soil 3 ~ 10% error; turbine, rotor, volumetric flowmeter moving parts constitute wear and tear, corrosion, or error, or can not work; electromagnetic flowmeter electrode, ultrasonic flowmeter transducer, thermal flowmeter thermoelectric anode contamination will reduce its sensitivity, increase the error; differential pressure flowmeter pressure hole constitute blockage, and so on. Of course, this process is slow, but never careless. And only need to pay attention to regular repair and constitute a guideline can also reduce (or eliminate) its impact.