What is A Flowmeter?

Figure 1: Different flowmeters.

Modern flowmeter is an exquisite instrument developed in the 18th and 19th centuries. The type of flowmeter are constantly improved with the change of society, the development of economy and the continuous progress of industry and the demand of the market increases. So, the development of flowmeter is closely related to all aspects of our life and production.

1. What It is

As the name suggests, it is an instrument that counts the volume of some measured streams in a certain time. Simply put, it is an instrument used to measure the fluid flow in pipelines or open channels.

Where there is material flow, people need flow measurement in order to know its quantity. The flow is divided into flow rate and total flow.

Flow rate: the amount passing through the effective section of closed pipeline or open channel in unit time. The material flowing through can be gas, liquid and solid.

Total flow: the cumulative amount of fluid flowing through the effective section of closed pipeline or open channel in a certain time interval (which can be a day, a week, a month or a year) is called the total flow. The total flow can be obtained by integrating the flow rate with time.

2. How Does A Flowmeter Work

Figure 2: The working principles of flowmeters are about total flow and flow rate.

When the measured medium flows through the flow meter, the impeller in the impact metering chamber rotates. In a certain flow range, the impeller speed is directly proportional to the flow. The impeller is a blade made of magnetic conducting stainless steel which approaches the sensor coil on casing when the impeller rotates. And it periodically changes the magnetic resistance of the magnetoelectric circuit of the sensor coil and the magnetic flux passing through the coil. It also generates a pulse electric signal proportional to the flow at the same time. After data processing, this signal displays the total flow and flow rate respectively.

3. Classification

Instruments used to measure flow rate or total flow are collectively referred to flow meters. Flowmeter is widely used in energy measurement, such as water, gas and other energetic working fluids. There are many kinds of flow meters, which can be divided into: differential pressure flow meter, rotameter, volumetric flow meter, turbine flow meter, electromagnetic flow meter, vortex flow meter, ultrasonic flow meter, mass flow meter, etc.According to the medium, it can also be divided into liquid flowmeter and gas flowmeter.

Figure 3: The electromagnetic flow meter and vortex flow meter.

4. Characteristics of An Ideal Flowmeter

Users always want to find an ideal flowmeter to do flow measurement. And flowmeter manufacturers try to manufacture ideal flowmeter to meet wider needs. After summing up all the advantages of thousands of flowmeters, we can indicate the conditions of ideal flowmeters as follows:

1. There are no obstructions on the tested parts;

2. The test piece can be clamped outside the pipeline and be moved freely to measure at any place without cutting off the pipeline and fluid;

3. The flow calculation equation of the flowmeter is simple and clear and it can be extrapolated to unknown fields without real flow verification;

4. Digital flowmete using frequency pulse to output signal, which is convenient for remote transmission, anti-interference and networking with computer;

5. The output signal of the flowmeter is not affected by the fluid flow characteristics;

6. High reproducibility;

7. Wide range and good linearity;

8. High reliability, appropriate price and uncomplicated maintenance mode;

9. There is no need for real flow calibration, or only need "dry calibration" and its calibration in one or two media can be extended to various media;

10. The output signal of the detector directly reflects the mass flow.

Figure 4: Using qualified flowmeter.

We can find that there is no flowmeter with all the above conditions so far. All flow meters have some of the above conditions more or less. All flowmeter manufacturers are trying their best to meet the above conditions for trial production of new products.

5. Importance of A Flowmeter

Flowmeter is one of the important instruments in industrial measurement, especially in the era of fast developing science and technology. Industry is a manifestation of the economic strength of a region. Flowmeter is one of the components of measurement science and technology. It is closely related to national economy, national defense construction and scientific research. Nowadays, the trend of automatic production society is more and more inseparable from flow measurement. And the status and role of flowmeter in national economic production is more prominent.

For example, the whole process of oil exploitation, transportation, refining and processing and trade sales is full of flowmeter. Once any link leaves the flowmeter for measurement, the production and sales of oil can not operate normally. And the treatment of urban sewage is inseparable from the flowmeter.

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