Manufacturers of small liquid flow meters compare small flow measurements with general flow measurements and summarize the following characteristics of small flow measurements.
Liquid flow meters are generally calibrated with water, while gas flow meters are calibrated with air. If it is known that certain physical properties between the actual measured fluid and the calibration fluid have regular changes in the displayed values, medium and large pipe flow meters are often corrected with appropriate coefficients. However, some small flow meters are greatly affected by fluid properties such as viscosity and require calibration based on actual fluid usage. Fortunately, the flow rate is small and it is not difficult to calibrate with actual fluids, but safety and environmental pollution should be taken into account when calibrating harmful fluids.
Generally, pipeline flow is turbulent flow, and flow meters are also designed for turbulent flow dynamics. However, small flow meters are often in laminar flow due to their small diameter.
If measuring clean gases and pure water, it is often not allowed for instrument components that come into contact with fluids to precipitate ions. For example, in semiconductor preparation, instruments cannot be made of metal or glass, only plastic can be used. It is also not allowed to mix abrasive dust particles from moving parts into the fluid. The flow channel of the flow meter should be as simple as possible, and there should be no retention (that is, the liquid accumulates abnormally in the body) to prevent the retention medium from deteriorating.
Due to the small diameter of the pipe, the viscosity increases, and fine bubbles in the liquid are prone to accumulate and grow during the flow of the pipeline system, resulting in unstable readings and decreased accuracy during measurement. The adhesion of dust in the fluid to the measuring element also affects the measurement value, for example, the deposition of an imperceptible adhesion layer on the float of a float flowmeter can also affect the reading.