Range refers to the spectrum between the maximum and minimum flow rates a flow meter can measure. Linearity denotes the relationship between the flow meter's output and the actual flow rates. In the selection and utilization of flow meters, both range and linearity are pivotal indicators.
1. Range
The range of a flow meter is determined by its design and principle. Different flow meters come with various ranges. Here are the ranges for several types of flow meters:
• Rotameter (Float-type flow meter): 0.05~3.5 m/s
• Other brands' paddle wheel flow meter: 0.3~10 m/s
• LORRIC AxleSense paddle wheel flow meter: 0.15~10 m/s
• Ultrasonic flow meter: 0.1~20 m/s
When choosing a flow meter, it's crucial to select one with an appropriate range based on the flow rate of the fluid being measured. A flow meter with too narrow a range cannot measure the fluid's maximum flow rate; conversely, if its range is too wide, the accuracy of the measurement will decrease.
2. Linearity
The linearity of a flow meter reflects the deviation between its output values and the actual flow rates.
Ideally, the output of a flow meter should be directly proportional to the actual flow rates, meaning the linearity would be 100%. However, in practice, all flow meters exhibit some degree of deviation.
The linearity of a flow meter is influenced by factors such as:
• The structure and principle of the flow meter
• Manufacturing process
• Operating environment
Generally, flow meters with simple structures and mature principles have higher linearity. Those manufactured with superior processes also tend to exhibit higher linearity. Moreover, in environments with significant temperature and pressure variations, a flow meter's linearity can decrease. The linearity of a flow meter affects its measurement accuracy. Flow meters with higher linearity provide more precise measurements.
When selecting a flow meter, it's important to choose one with appropriate linearity based on the required measurement accuracy. If high measurement accuracy is necessary, a flow meter with high linearity should be selected.
3. The Relationship Between Flow Meters, Range, and Linearity
The range and linearity of a flow meter are interrelated indicators.
Generally, flow meters with larger ranges tend to have lower linearity. This is because, at the extremes of the range, the deviation between the flow meter's output and the actual flow rates becomes greater.
When choosing a flow meter, it's essential to consider both range and linearity. Within the constraints of the required range, selecting a flow meter with higher linearity is advisable.